TF250061: The following site could not be attached to Team Foundation Server: The site is already associated with a team project on an installation of Team Foundation Server with a different ID.

Explanation:

I had this problem when I migrated TFS 2010 collection to TFS 2012 instance and having the collection online on both TFS 2010 and TFS 2012 instances in parallel.

Solution:

To fix the problem, you need to disable the team project portal links either on TFS 2010 or TFS 2012 collection --> Team projects and run the SharePoint repair on the APP TIER using TFS administration console.

 Following are the steps I followed to fix the error in TFS 2012 instance

1. Open Team Explorer in Visual Studio --> Connect to TFS 2010 instance --> Select the team project that needs the fix --> goto "Portal Settings" --> Unchecked the "Enable Team Project Portal checkbox" --> click OK

2. Login to TFS 2012 App Tier --> Open TFS Administration console --> Select "Share Point Web Applications" --> Select the SharePoint URL --> click "Repair Connection" --> Repair option

All the permissions and connections to the team projects Share point sites should succeed.

(Optional)

3. Login to TFS 2010 App Tier --> Open TFS Administration console --> Select "Share Point Web Applications" --> Select the SharePoint URL --> click "Repair Connection" --> Repair option

All the permissions and connections to the team projects Share point sites should succeed.