Telerik NuGet package source Showing Unauthorized 401 error

[Camron]

I am trying to follow the instructions on this URL: https://www.telerik.com/aspnet-core-ui/documentation/getting-started/video-onboarding

I added the source to the Nuget settings with this URL: https://nuget.telerik.com/v3/index.json

When I go to the NuGet package manager and select the Telerik. The first time I did enter credentials but I got a 

[Telerik] Unable to load the service index for source https://nuget.telerik.com/v3/index.json.
  Response status code does not indicate success: 401 (Unauthorized).

Since then I have tried removing and re-adding the source but I always get the same error and I can't re-enter my credentials to see if that is the issue. 

How do I check if I entered my credentials wrong and How do I fix this so I have access to the telerik nuget source?

[Lance | Senior Manager Technical Support]

Hi Cameron, this sounds like you have some credentials cached, or you have a nuget.config with incorrect credentials. I have two things for you to try:

1. Close any IDE/tooling that might be using NuGet.
2. Open the Windows Credential Manager app
3. Switch to the Windows Credentials tab
4. Scroll down and locate two items;  "nuget.telerik.com" and "VSCredential_nuget.telerik.com"
5. Edit both of them... or delete them and re-enter the credentials when VS tries to load the source again.

Now, let's see if you have anything in a nuget.config.

1. First, lets check the default global file, open %appdata%/NuGet/NuGet.Config
   1. Do you have a packageSourceCredentials section for the Telerik source?
   2. If yes, either delete it or update it (if you update it, do not use your password, use a Telerik NuGet Key instead)
2. Next, lets check for a nuget.config in your source code. This is a very common approach to also include a nuget.config file in the sync source code (it's usually in the folder next to the sln file, but can be in the project folder or higher up).
   1. In that project-specific config file, do you see a packageSourceCredentials section like mine? => src/NuGet.Config#L21-L26 
   2. If yes, this is used for building the code in CI/CD, there is typically an environment variable placeholder. You can add those two env vars to your OS user's environment and it will be used when .NET SDK or VS tries to connect to that exact source.

I would personally just delete all the items in Credential Manager and let VS2022 re-save them the next time you open a project. Keep in mind that if you also have a nuget.config with a packageSourceCredential, that will be used instead.