Adding a new TFS server resulting in error: "Server already exists in the list below"

While trying to add a TFS server to Visual Studio 2017, I encountered an issue where it claims that the server already exists in the list. However, it does not.

The only thing that I can think of that could cause it to think that the server is in the list, is that the two servers used to be one. This was not an issue with Visual Studio 2015.

The TFS servers are both 2015 update 3.

Give a try with directly using IP address instead of server name when you are adding Team Foundation Server in Visual Studio. Something like:

http://192.168.0.1:8080/tfs

You can also find your Team Foundation Server 2015 GUID Info in the below location:

 C:\Program Files\Microsoft Team Foundation Server 14.0\Application Tier\Web Services\web.config

There should be a value like

Then you could compare the GUIDs of the two servers, change one of them, and re-register the db. For more details about it, take a look at this blog post: How to find Team Foundation Server(TFS) GUID Info