Recently every time I tried to connect to Azure in the Visual Studio Server Explorer I kept getting this Multiple Matching Tokens error.
Trying to reconnect always gave me the Already Signed In message.
Selecting either the Remain signed in or Sign out and sign in with a different account didn't help, with both I just got the same error again.
Trying this for a couple (a bit too often actually) times with no success, I finally selected the Manage subscription option and there selected Sign out
After signing out using that option, restarting Visual Studio, I then Connection to Azure in the Server Explorer again and it finally worked :)