ALTER TABLE DROP COLUMN - server status 'Stopped'
Open another connection to the same server (just click the home screen tile again, which you used to open the current connection). It will tell you if the server is available or not. Maybe the UI got stuck somehow and did not update properly when the operation ended. Don't forget the connection could also have timed out and you need to re-connect (which usually happens automatically, but somethings things just go wrong).