# Error: Could not load File **URL:** \ **Category:** Studio\ **Tags:** question, studio\ **Created:** [September 8, 2026, 3:38pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630 "2026-09-08T15:38:50Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Nick\_Scott](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/nick_scott/32/551942_2.png) [@Nick\_Scott](https://forum.uipath.com/u/Nick_Scott)\ **Post date:** [September 8, 2026, 3:38pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/1 "2026-09-08T15:38:50Z")
Hello, again, 3rd time today šŸ™‚ A student sees the following error when running a workflow for the second time. Yep, first time runs fine, second time it wonā€™t run. Edit: change actual name to just name Error] System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ā€”\> System.IO.FileLoadException: Could not load file or assembly ā€˜C:\Users\name\Documents\UiPath\Working with Files.local\install\Working with Files\_Expressions\_Main.dllā€™. An Application Control policy has blocked this file. (0x800711C7) at Working\_with\_Files.Main..ctor() at Working\_with\_Files.Main..ctor() at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions) ā€” End of inner exception stack trace ā€” at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions) at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object args, CultureInfo culture) at System.Activator.CreateInstanceInternal(String assemblyString, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object args, CultureInfo culture, Object activationAttributes, StackCrawlMark& stackMark) at System.Activator.CreateInstance(String assemblyName, String typeName) at UiPath.MapFilePathToActivity\_93063903935340c8aab522ec692cb083.MapFilePathToActivity(String relativePath) at UiPath.Executor.WorkflowLoader.GetWorkflowActivity(String xamlRelativePath, Assembly assembly) in D:\a\1\s\Robot\UiPath.Executor.Core\NetCore\WorkflowLoader.cs:line 112 at UiPath.Executor.WorkflowLoader.\<\>c\_\_DisplayClass14\_0.b\_\_0(WorkflowFile workflowFile) in D:\a\1\s\Robot\UiPath.Executor.Core\NetCore\WorkflowLoader.cs:line 86 at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory) at UiPath.Executor.Core.WorkflowBuilder.Build() in D:\a\1\s\Robot\UiPath.Executor.Core\WorkflowBuilder.cs:line 79 at UiPath.Executor.RobotRunner.BuildWorkflow() in D:\a\1\s\Robot\UiPath.Executor.Core\RobotRunner.cs:line 360 at UiPath.Executor.RobotRunner.InitWorkflowApplication() in D:\a\1\s\Robot\UiPath.Executor.Core\RobotRunner.cs:line 344 at UiPath.Executor.RobotRunner.ExecuteJob(Boolean preLoaded) in D:\a\1\s\Robot\UiPath.Executor.Core\RobotRunner.cs:line 629 ---
**Author:** ![MayureshOfficial\_45](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/mayureshofficial_45/32/572160_2.png) [@MayureshOfficial\_45](https://forum.uipath.com/u/MayureshOfficial_45)\ **Post date:** [September 8, 2026, 3:56pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/2 "2026-09-08T15:56:17Z")
Hi @Nick_Scott, The important part of the error is: **ā€œAn Application Control policy has blocked this file.ā€** This appears to be a Windows security or Application Control policy issue rather than a UiPath workflow issue. Please ask the IT administrator to check whether **AppLocker, Windows Defender Application Control (WDAC), or another security policy** is blocking the generated `_Expressions_Main.dll` file. You can also try: 1. Close UiPath Studio. 2. Delete the projectā€™s `install` folder. 3. Reopen the project and run it again. 4. Check whether the project folder or generated DLL files are being blocked by Windows Security/AppLocker. 5. Try running the project from a different local folder to confirm whether it is a folder or policy restriction. Since the first run works but the second run fails, the generated assembly may be getting blocked after it is created. It would also be useful to check the Windows Event Viewer or security logs to identify which Application Control policy is blocking the DLL. ---
**Author:** ![Monali\_Vekariya](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/monali_vekariya/32/264397_2.png) [@Monali\_Vekariya](https://forum.uipath.com/u/Monali_Vekariya)\ **Post date:** [September 9, 2026, 5:56am UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/3 "2026-09-09T05:56:13Z")
Hi @Nick_Scott This looks like a **Windows Application Control/AppLocker** issue. The error specifically says the generated `.dll` is being blocked. Try running the project from a different folder. If the issue remains, the IT administrator needs to **allowlist the UiPath project/install folder or the generated DLL**. Since the first run works and the second fails, it is likely a security policy rather than a workflow issue. ---
**Author:** ![Jasmin\_Bar](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/jasmin_bar/32/498877_2.png) [@Jasmin\_Bar](https://forum.uipath.com/u/Jasmin_Bar)\ **Post date:** [September 9, 2026, 5:59am UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/4 "2026-09-09T05:59:13Z")
Hi @Nick_Scott , Try these steps : 1. Close UiPath Studio. 2. Delete the projectā€™s **.local** , **bin** , and **obj** folders. 3. Reopen the project and run it again to regenerate the DLLs. 4. Check **Windows Security ā†’ App & Browser Control** and see if **Smart App Control** or **Application Control** is blocking the file. 5. If managed by a school/company policy, ask the IT administrator to whitelist UiPath-generated files or the project folder. 6. Move the project to a trusted local folder (for example, `C:\UiPathProjects`) instead of Documents/OneDrive and test again. Thanks ---
**Author:** ![Nick\_Scott](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/nick_scott/32/551942_2.png) [@Nick\_Scott](https://forum.uipath.com/u/Nick_Scott)\ **Post date:** [September 9, 2026, 10:26am UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/5 "2026-09-09T10:26:15Z")
thanks for all the suggestions guys, but this is a studentā€™s personal pc so thereā€™s no IT admin šŸ™‚ Iā€™ll try checking windows security and let you know if I manage to solve it ---
**Author:** ![Roshan.Manchanayake](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/roshan.manchanayake/32/180895_2.png) [@Roshan.Manchanayake](https://forum.uipath.com/u/Roshan.Manchanayake)\ **Post date:** [September 9, 2026, 1:05pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/6 "2026-09-09T13:05:41Z")
Hi @Nick_Scott, The most important part of the exception here is actually not `TargetInvocationException` or the UiPath workflow stack trace. Itā€™s this: `An Application Control policy has blocked this file. (0x800711C7)` And the file being blocked is the generated: `_Expressions_Main.dll` Since the workflow runs successfully the first time and fails on the second run, Iā€™d investigate the Windows application-control/security layer rather than the workflow itself. Iā€™d check: - Windows Event Viewer ā†’ CodeIntegrity / AppLocker-related logs - Whether WDAC/AppLocker or another endpoint security product is blocking the generated DLL - Whether the UiPath project is running from a folder covered by an application-control policy - Whether moving the project temporarily to another local directory changes the behaviour - Whether deleting the `.local\install` output and rebuilding causes the DLL to be generated again before being blocked If this is a managed/student machine, Iā€™d also ask the administrator whether a recent security policy was applied. The fact that the first execution succeeds but the second fails makes me particularly interested in what happens to the generated DLL between those two executions. If you can share the corresponding CodeIntegrity/AppLocker event for the blocked DLL, that should tell us much more than the UiPath stack trace. ---
**Author:** ![Nick\_Scott](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/nick_scott/32/551942_2.png) [@Nick\_Scott](https://forum.uipath.com/u/Nick_Scott)\ **Post date:** [September 10, 2026, 1:47pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/7 "2026-09-10T13:47:27Z")
we checked event viewer and found the following in : Microsoft ā†’ Windows ā†’ CodeIntegrity ā†’ Operational Code Integrity determined that a process (\Device\HarddiskVolume3\Program Files\UiPathPlatform\Robot\26.0.201-cloud.24739\UiPath.Executor.exe) attempted to load \Device\HarddiskVolume3\Users\RPala\Documents\UiPath\Working with Files\.local\install\Working with Files\_Expressions\_Main.dll that did not meet the Enterprise signing level requirements or violated code integrity policy (Policy ID:{0283ac0f-fff1-49ae-ada1-8a933130cad6}). ![image](https://global.discourse-cdn.com/uipath/original/4X/2/9/a/29a3ec6937051071c8cac74fd773e69b64703390.png) Code Integrity determined that a process (\Device\HarddiskVolume3\Program Files\UiPathPlatform\Robot\26.0.201-cloud.24739\UiPath.Executor.exe) attempted to load \Device\HarddiskVolume3\Users\RPala\Documents\UiPath\Working with Files\.local\install\Working with Files\_Expressions\_Main.dll that did not meet the Enterprise signing level requirements same opcode the dependency is system activities, version 26.8.0 latest causes this issue, the old version 22.10.4 does not produce the issue. ---
**Author:** ![Roshan.Manchanayake](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/roshan.manchanayake/32/180895_2.png) [@Roshan.Manchanayake](https://forum.uipath.com/u/Roshan.Manchanayake)\ **Post date:** [September 10, 2026, 7:18pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/8 "2026-09-10T19:18:04Z")
Hi @Nick_Scott, Thatā€™s a very useful finding. At this point we can narrow this down considerably. The Code Integrity event confirms that Windows is blocking the generated `_Expressions_Main.dll` when `UiPath.Executor.exe` tries to load it: `...\.local\install\Working with Files\_Expressions\_Main.dll` And the fact that changing `UiPath.System.Activities` from **26.8.0 to 22.10.4** makes the problem disappear is a strong indication that the issue is related to the newer package/runtime combination rather than the workflow itself. I would do one more controlled test before settling on the workaround: **1. Try 26.8.1 if it is available in your feed.** UiPath released System Activities 26.8.1 on September 4, shortly after 26.8.0. The current release notes show that 26.8.1 contains fixes for issues introduced in 26.8.0. **2. If 26.8.1 still produces the same Code Integrity event** , keep the 22.10.4 version as the known-good baseline. **3. Compare the generated `_Expressions_Main.dll` between the working and failing versions** , if possible. The important question is whether the assembly generated/loaded with 26.8.0 has different signing/metadata characteristics that cause the Enterprise Code Integrity policy to reject it. **4. Keep the Code Integrity event details** , especially the Policy ID: `{0283ac0f-fff1-49ae-ada1-8a933130cad6}` That gives you something concrete to provide to UiPath Support if 26.8.1 doesnā€™t resolve it. So I agree that the System Activities version is now the strongest lead. I just wouldnā€™t classify 26.8.0 itself as the confirmed root cause until we test 26.8.1 or reproduce the same behaviour in another environment with the same Code Integrity policy. Nice investigation ā€” the Event Viewer entry was much more useful than the original UiPath exception. ---
**Author:** ![Nick\_Scott](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/nick_scott/32/551942_2.png) [@Nick\_Scott](https://forum.uipath.com/u/Nick_Scott)\ **Post date:** [October 7, 2026, 10:04am UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/9 "2026-10-07T10:04:58Z")
An interesting new development to this issue. I am current investing the ā€˜learn moreā€™ button, but in the meantime has anyone else seen this? ![image](https://global.discourse-cdn.com/uipath/original/4X/1/f/4/1f461ab7f8348d31faac680df08c6ce2f307c105.png) ---
**Author:** ![imad-pro](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/imad-pro/32/571822_2.png) [@imad-pro](https://forum.uipath.com/u/imad-pro)\ **Post date:** [October 7, 2026, 7:26pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/10 "2026-10-07T19:26:26Z")
0x800711C7 points to Windows Smart App Control or Code Integrity blocking the generated UiPath expression DLL. Iā€™d confirm the block in Windows Security first and test with a current UiPath.System.Activities version before changing SAC settings, since turning SAC off is not easily reversible. ---
**Author:** ![Nick\_Scott](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/nick_scott/32/551942_2.png) [@Nick\_Scott](https://forum.uipath.com/u/Nick_Scott)\ **Post date:** [October 7, 2026, 11:10pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/11 "2026-10-07T23:10:35Z")
> [@imad-pro](#): > > test with a current UiPath.System.[Activities](https://docs.uipath.com/activities/docs/introduction) version Thanks for your response ā€¦ which is interesting, because we are using the latest version, that at the same time is causing different issues leading to the suggestion that we should use version 24 - _I think someone else suggested version 22_. Will these bugs be fixed do you think, or are you suggesting itā€™s actually windows that is at fault here? ---
**Author:** ![pravinraj.vincent](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/pravinraj.vincent/32/152254_2.png) [@pravinraj.vincent](https://forum.uipath.com/u/pravinraj.vincent)\ **Post date:** [October 16, 2026, 12:38pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/12 "2026-10-16T12:38:21Z")
Hi @Nick_Scott, itā€™s Windows doing the blocking, so I wouldnā€™t wait on a package fix. Smart App Control only loads code that Microsoft trusts or thatā€™s signed, with no per-app exception, and the DLLs Studio compiles for each project are unsigned unless you set a Dynamic DLLs Certificate under Settings \> Locations. On your own PC, the practical fix is turning Smart App Control off in Windows Security \> App & browser control, and recent Windows updates let you turn it back on later without reinstalling. [Studio settings](https://docs.uipath.com/studio/standalone/latest/user-guide/configuring-studio-settings) ---
**Author:** ![Nick\_Scott](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/nick_scott/32/551942_2.png) [@Nick\_Scott](https://forum.uipath.com/u/Nick_Scott)\ **Post date:** [October 16, 2026, 1:25pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/13 "2026-10-16T13:25:55Z")
thanks for your response. Interesting that it happens on my studentā€™s machine, but works fine on my machine. ---
**Author:** ![pravinraj.vincent](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/pravinraj.vincent/32/152254_2.png) [@pravinraj.vincent](https://forum.uipath.com/u/pravinraj.vincent)\ **Post date:** [October 26, 2026, 1:50pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/14 "2026-10-26T13:50:16Z")
Hi @Nick_Scott, that difference fits Smart App Control. Windows turns it on automatically on some PCs and switches it off on its own on others, for example enterprise-managed machines or ones it sees being used for development. So two PCs on the same Windows version can behave differently. On the studentā€™s PC, open Windows Security \> App & browser control and check Smart App Control. If itā€™s On, thatā€™s whatā€™s blocking the compiled DLL, and thereā€™s no per-app exception for it. > **[Smart App Control Frequently Asked Questions | Microsoft Support](https://support.microsoft.com/en-us/windows/security/threat-malware-protection/smart-app-control-frequently-asked-questions)** > > Frequently asked questions (FAQs) about Smart App Control, a Windows feature designed to block malicious, untrusted, or potentially unwanted apps from running on your device. ---
**Author:** ![Ankit9510](https://sea2.discourse-cdn.com/uipath/user_avatar/forum.uipath.com/ankit9510/32/512761_2.png) [@Ankit9510](https://forum.uipath.com/u/Ankit9510)\ **Post date:** [October 26, 2026, 3:11pm UTC](https://forum.uipath.com/t/error-could-not-load-file/5775630/15 "2026-10-26T15:11:20Z")
Hi @Nick_Scott, About why it works on your PC but not on your studentā€™s: the Event Viewer message says Windows blocked the \_Expressions\_Main.dll that Studio creates in the .local\install folder. So Windows security is blocking it, not your workflow. This looks like the Smart App Control (SAC) that @imad-pro and @pravinraj.vincent mentioned. Please check both PCs: 1. Open Windows Security 2. Go to App & browser control 3. Open Smart App Control settings and see if it is On, Evaluation or Off If it is On only on your studentā€™s PC, that could explain the difference. I canā€™t be 100% sure, so please confirm. If it is On, you can turn it Off and run the project again. Please read Microsoftā€™s note on SAC first, because some people in this thread said it canā€™t be easily turned On again. Another option is the Dynamic DLLs Certificate setting in Studio (Backstage View \> Settings \> Locations). It signs the DLLs Studio generates. You need a code-signing certificate that Windows trusts for this.