Continuous Error in UiPath Studio After Update

After updating UiPath studio 2 days ago(230628), I am continuously encountering the error shown in the attached image. (When I try to debug the file, the window that says “Validating the project’s error…” keeps infinitely loading.)

Even when there is no object in the variable, I keep getting this error and I’m unable to find a solution, so I’m posting this question in the forum. Furthermore, the same error occurs in the projects that I had already created and have been using. (For reference, the project that is currently having an error is a copied and pasted version of an existing project file. I only changed the name in the json file.)

Any help would be greatly appreciated…

Error details:

Error: System.Exception: Object reference not set to an instance of an object.
at System.Activities.Presentation.Validation.ValidationService.MarkParents(ValidationError validationError, IEnumerable1 errorParents, ModelItem source)
at System.Activities.Presentation.Validation.ValidationService.MarkError(ValidationError validationError, List1 errorSourcePath, ModelItem source)
at System.Activities.Presentation.Validation.ValidationService.MarkErrors(ICollection1 errors, ValidationReason reason, Activity rootActivity)
at System.Activities.Presentation.Validation.ValidationService.OnValidationWorkCompleted(Tuple3 input)
at System.Activities.Presentation.Validation.BackgroundValidationSynchronizer`1.<>c__DisplayClass26_0.b__0()
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler), HResult -2147467261


Studio 2023.6.0-beta.13314 - 2023. 6. 27.
Community License
Per User installation
Microsoft Windows 11 Pro 64-bit

The error continues to occur even in this environment:
Studio 2023.6.1-beta.13324 - June 28, 2023
Community License
Per User installation
Microsoft Windows 11 Pro 64-bit

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Hi @jay.jmee

When updating the studio some variables are not initialized properly. In this case only the error is throwing. Check the variables are passed properly or not.

Hope it helps!!

Hi @jay.jmee
Some general suggestions to troubleshoot the issue you’re experiencing after updating UiPath Studio:

  1. Clear Studio Cache: Clearing the UiPath Studio cache can help resolve certain issues. Close UiPath Studio and navigate to the %userprofile%\.nuget\packages folder on your computer. Delete any folders related to UiPath packages. Then, restart UiPath Studio and try running/debugging the project again.
  2. Repair/Reinstall UiPath Studio: If clearing the cache doesn’t resolve the issue, you can try repairing or reinstalling UiPath Studio. Go to “Control Panel” → “Programs” → “Programs and Features” (Windows) or “Applications” (Mac) and select UiPath Studio. Choose the repair option or uninstall and then reinstall UiPath Studio.
  3. Check for Dependency Conflicts: It’s possible that some dependencies in your project are conflicting or causing issues. Make sure you have the latest versions of all required dependencies. Additionally, check if any custom activities or packages used in your project need to be updated to be compatible with the new version of UiPath Studio.
  4. Update Activities and Packages: Ensure that all activities and packages used in your project are updated to their latest versions. Outdated activities or packages might not be fully compatible with the new version of UiPath Studio, causing issues during debugging.
  5. Review Logs: Check the UiPath Studio logs for any error or warning messages related to the project. The logs can provide more insights into the cause of the issue. You can find the log files in the %localappdata%\UiPath\Logs directory.
  6. Contact UiPath Support: If the issue persists and none of the above steps resolve it, it’s best to contact UiPath Support for further assistance. Provide them with detailed information about the error, steps to reproduce it, and any relevant log files.

Remember to backup your projects before attempting any troubleshooting steps to avoid any potential data loss.


Hello, I have some additional information…!

I’ve been trying to enable and disable each activity one by one. But, an error occurs simply when the “On Element Appear” activity exists, regardless of any other conditions.

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The message “object reference not set to an instance of an object” means that you are referring to an object the does not exist or was deleted or cleaned up . It’s usually better to avoid a NullReferenceException than to handle it after it occurs.

If you are experiencing an error specifically when the “On Element Appear” activity exists in your workflow, there could be a few reasons for this issue. Here are some suggestions to help you troubleshoot and resolve the problem:

  1. Check the Selector: The “On Element Appear” activity relies on a selector to identify the element on the screen. Ensure that the selector is correctly configured and is targeting the desired element. Verify that the selector is not too specific or too general, as this can lead to issues with identifying the element.
  2. Validate the Element: Make sure that the element you are trying to capture with the “On Element Appear” activity exists on the screen and is accessible at the time the activity runs. If the element is dynamically loaded or takes some time to appear, consider adjusting the timeout settings of the activity to allow sufficient time for the element to appear.
  3. Verify Application or Browser Compatibility: The “On Element Appear” activity may encounter issues if it is not fully compatible with the application or browser you are working with. Ensure that you are using a supported version of the application or browser and that any necessary extensions or add-ons are installed and enabled.
  4. Check for Dependencies: Some activities, including the “On Element Appear” activity, may rely on other dependencies or packages. Make sure that you have the necessary packages installed and updated to the correct versions. Check the activity documentation for any specific dependencies or prerequisites.
  5. Review Error Details: When the error occurs, check the error message or details provided by UiPath Studio. It may give you more specific information about the cause of the error, such as an invalid selector or a timeout issue. Reviewing the error details can help you pinpoint the problem and take appropriate actions.
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I’ve found the methods that are causing the NullReferenceException error in the log.

I haven’t used methods like ‘GetSymbol’ from the ‘ForEachFileAssistant’ class before. Where should I look for this?

The following text is a response from ChatGPT.

The methods that have been mentioned so far causing the NullReferenceException error are:

IsTypeSupportedForSingleFile(Type type) - This method is part of the UiPath.Activities.System.Design.Business.FileInfoCompatibilityRules class and checks whether a specific type of file is supported for single file.

GetSymbol(Object context, Type type) - This method is part of the UiPath.Activities.System.Design.Business.ForEachFileAssistant class and retrieves the symbol (indicator) for the given context and type.

A NullReferenceException error in these methods means that the method is trying to reference a null object. To resolve this issue, you should debug your program to identify where this null reference is occurring. If the object at this location has not been initialized, then you should add the appropriate initialization code.

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I’m experiencing the same issue as @jay.jmee.

As mentioned, having an empty file and adding ‘On Element Appear’ will cause the error (the element as yet to be set).

After setting the element, clearing the cache, updated packages, reinstalled Studio, the error persists.

Testing the same on a Windows-Legacy project, the error does not appear.

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@jay.jmee & @Waz

Try giving a selector first and check…

If that does not work then change the system packages version to any stable version and chekc if the error persists

Alternately…try renaming the project.json and reload the project again

It would be helpful if you can click on details or open the logs and see the error details


Hey guys!

I got the same issue after Studio update.

After reading this thread, I replaced “On element appear” by “Check app state”.

It works fine.



This topic was automatically closed 3 days after the last reply. New replies are no longer allowed.

Additionally, Studio 2023.10 fixed the issue.