After applying update 2 VisualStudio 2015 Enterprise can't connect to TFS - exception TF205020

VisualStudio 2015.1 Enterprise/TFS integration worked fine until VS2015 update 2 was applied.

Reinstalling/repairing VisualStudio didn't fix the issue, keep getting:

TF205020: Could not connect to server ...... The server returned the following error:

Could not load type Microsoft.VisualStudio.Services.WebApi.Utilities.UserAgentUtility' from assembly 'Microsoft.VisualStudio.Services.WebApi, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

SETUP:

VS Enterprise 2015.2 TFS 2015.2

We had the same issue here. Reinstalling Visual Studio 2015 after deleting cache, user profile folders and registry settings didn't help us. It looks like a TestComplete 11.31 installation installs some assemblies in the GAC which conflicts with Visual Studio 2015 Update 2. We fixed the issue comparing two almost identical systems (one with and one without TestComplete) and these assemblies we deleted from the %WINDOWS%\Microsoft.NET\assembly folder:

• Micorosft.VisualStudio.Services.Client
• Micorosft.VisualStudio.Services.Common
• Micorosft.VisualStudio.Services.Integration
• Micorosft.VisualStudio.Services.WebApi

But the problem still existed. After removing:

• Microsoft.TeamFoundation.Client
• Microsoft.TeamFoundation.WorkItemTracking.Common

the problem was gone!

I hope this will help your issue...