You are not authorized to access when trying to connect to TFS account in Visual Studio 2015

To solve this problem you have to clean the cache folder on your machine.

1. Press Win + R together to open the Run window

   

2. Type in %UserProfile%\AppData\Local and click on OK

   

3. Navigate to the Microsoft\Team Foundation\6.0\Cache folder and delete all contents

   

4. Restart Visual Studio and Re-Open your solution.
5. The error message will disappear and all should be working again.