How to Get Light Cover Off!
It likely has a spring / pressure / snap connector and is not a screw on type of fitting. We can tell that it's not a screw on since it's the same no matter how much or what direction you turn it. Try carefully prying it to one side or the other from the top of the light cover while holding the light base so to not put force on the connection of the fixture to the wall. More than likely it will just pop out. Don't be shy with the force, it might take a little, while of course being careful not to break or damage anything