In many cases, Studio will be unable to select UiElements from a browser or desktop app window. Installing and using the Inspect.exe tool can help us determine if this is an issue with Studio itself or if the machine is unable to see UiElements from the window in question in general.
Please click here to install the Windows 10 sdk kit*:
After install, navigate to C:\Program Files (x86)\Windows Kits\10\bin\10.0.19041.0\x64\Inspect.exe. (if 10.0.19041.0 does not exist, try navigating to the next highest version folder)
When Inspect.exe opens, open your browser or windows application and try hovering over the elements in question. A tree like structure with elements that change and look similar to UiExplorer should appear. If not, then the machine's ability to target UiElements in general is being blocked and this issue extends beyond UiPath functionality.
*Note: As validated on the software and hardware requirements of the download page, this kit is not restricted to the Windows 10 OS and will work on variations of Windows Server and etc. Make sure that you have the .NET framework (for the case this article was created from, the version needed was 4.7.2) installed on your machine else you may run into issues when trying to locate the Inspect.exe folder.