This is probably happening because the stored credentials are wrong, or are not successfully saving. The best option here is to just delete them entirely.
1. Close Visual Studio
2. Open the windows Credentials Manager
3. Switch to the Windows Credentials tab
4. Scroll through the list and locate every "nuget.telerik.com" item and delete it
5. Reopen Visual Studio and try installing a package again
At this point, there are no stored credentials, so you'll get a sign in popup again when Visual Studio's nuGet Package Manager tries to connect to the Telerik NuGet server.
A couple notes:
- Use the Telerik account that has a license to the product you're trying to install
- If you change your Telerik password, you will need to update that credential
Lance | Technical Support Engineer, Principal
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