Your project uses GAC referenced assemblies

Hi, Ali,

According to the provided information, it wouldn't be easy to determine what causes this undesired behavior on your end. However, I would like to ask you to check the references to all Telerik controls in your project and make sure that they are the same version considering the suffix as well (.20 or .40) since it is usually the most common reason for such a behavior after upgrading. Better yet, you can remove all references and add them anew by using the DLLs from your fresh installation: https://docs.telerik.com/devtools/winforms/installation-and-upgrades/updating-assemblies-in-a-project 

Delete the license.licx file. After that, you should rebuild your project, close Visual Studio and open it again to make sure that no references are kept in the memory by Visual Studio. Ensure that no old versions are available in GAC: https://docs.telerik.com/devtools/winforms/knowledge-base/examine-the-gac 

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik