NuGet Troubleshooting with JustMock

Updated on Feb 18, 2026

Telerik NuGet Feed Troubleshooting

This article summarizes the issues that may occur when you work with JustMock and the online Telerik NuGet feed, and their solutions.

Regardless of the cause for the issue, it is recommended that you start from the section on the commonly occurring issues.

• Tips for handling common NuGet issues
• Removing stored credentials
• Error 503 Service Unavailable
• Error Unable to resolve ... . PackageSourceMapping is enabled
• Error Failed to retrieve information about ... from remote source

Telerik NuGet Feed Status

Visit status.telerik.com to check the status of the Telerik NuGet server. The top section shows manually logged incidents with possible updates or workaround suggestions. The System Metrics section provides real-time automated diagnostics.

Tips for Handling Common NuGet Issues

The most common reasons for issues with the private Telerik NuGet feed are related to:

• Authentication and credentials.
• Licensing. For example, requesting commercial packages with a trial license or vice-versa.
• Missing or wrong local configuration (NuGet.Config).
• Network connectivity issues, including proxies and firewalls.

Errors like Unable to load the service index for source https://nuget.telerik.com/v3/index.json don't indicate the exact cause of the problem. In such cases, check the additional error information which usually provides an error code.

To verify if you can access the Telerik NuGet server and the expected packages, open the https://nuget.telerik.com/v3/search?q=justmock&prerelease=true&skip=0&take=100&semVerLevel=2.0.0 URL directly in the web browser and enter username api-key and your Telerik API Key as password in the prompt.

As a result, you will see a JSON output with the NuGet packages and versions that are available for you. You can search for JustMock.Commercial or Telerik.JustMock.Console.

If the above URL doesn't open, you have either come across a local networking issue or the NuGet server is down.

If you can access the feed in the browser, but you do not see the packages in Visual Studio, most likely the problem is caused by entering wrong credentials. Make sure your saved Telerik API Key is correct. Also, check to see if you have a NuGet.Config file in the project. That will add its package sources and package source credentials. If there is one, ensure that it contains the correct values for the Telerik NuGet feed. For example, you can store your credentials as plain text in the NuGet.Config file using api-key as the username and your API key as the password. For improved security, you can use environment variables to store sensitive information like your API key what wouold allow you to reference the credentials in the NuGet.Config file without exposing them directly.

Removing Saved Credentials

If you suspect that your saved credentials are wrong, use the following steps to remove them from Windows and, then, add the correct ones:

1. Remove the saved credentials in the Windows Credential Manager. These credentials will appear as nuget.telerik.com or VSCredentials_nuget.telerik.com entries.
2. Remove the Telerik NuGet package source from Visual Studio.
3. If you have added the Telerik package source by NuGet CLI, try to remove it from the CLI by running the following commands:
   • dotnet nuget list source
   • dotnet nuget remove source
4. Check if you have any credentials stored in %AppData%\NuGet\Nuget.Config. If so, remove them.
5. Try to reset the Visual Studio user data by forcing NuGet to ask for authentication.
6. Restart Visual Studio.
7. Enter the Telerik NuGet package source again through Visual Studio or CLI. If you are using the feed in a .NET Core application, store your credentials as plain text.
   • Option 1 - When using CLI to add the package source, you need to use the --store-password-in-clear-text flag
   • Option 2 - When using a nuget.config file, the key should be ClearTextPassword:
   XML

   <packageSourceCredentials>
     <Telerik>
       <add key="Username" value="api-key" />
       <add key="ClearTextPassword" value="YOUR_TELERIK_API_KEY" />
     </Telerik>
   </packageSourceCredentials>

Error 503 Service Unavailable

If you get a message like Unable to load the service index for source and error 503 (Service unavailable), check the Telerik NuGet server health at the Telerik live services status page.

In urgent cases, download the NuGet packages from your Telerik Account Downloads page. Then, set up a local NuGet feed.

Unable to Resolve Package due to PackageSourceMapping

Incorrect package source mapping can result in errors similar to:

NU1100 Unable to resolve 'Telerik... (>= ...)' for 'net...'. PackageSourceMapping is enabled, the following source(s) were not considered: ...

One solution is to check the Package Source Mapping settings in Visual Studio, or review all applicable NuGet.Config files on the machine. Then, adjust the package source mapping configuration. You can refine your mapping to account for JustMock and other Telerik products like the following example.

Failed to Retrieve Information from Remote Source

An attempt to use the obsolete Telerik NuGet v2 feed after November 2024 will result in an error:

Failed to retrieve information about 'JustMock.Commercial' from remote source 'https://nuget.telerik.com/nuget/FindPackagesById()?id='JustMock.Commercial'&semVerLevel=2.0.0'.

The solution is to use the Telerik NuGet v3 feed.

Another possible reason for the same error is an incorrect NuGet feed URL.