Thank you for contacting us.
Have you tried the previously proposed actions? Was there any change in the behavior?
What is your Visual Studio version and do you observe the issue for a particular project or it is the same if a new one is created as well?
Unfortunately this is an inconsistent behavior which we usually could not replicate. Please try reset the extension named Telerik.TestStudio.TestAdapter from the Tools - Extension and Updates. First disable it and try to enable it.
If that doesn't help re-registering the extension may also help. Unfortunately this is only possible via re-installing the product.
Please give a try to the above suggestions and let me know if there is any change in the behavior. Please provide some further info on the topics listed above as well - this might be helpful to find a solution. Thanks in advance for your time and cooperation!
Telerik by Progress