A while ago, I had to get a new battery in my car, a 2002 VW Cabrio. The stereo was working fine before then, but now it won't work. When I turn it on, it says "safe". None of the buttons do anything. No music turns on and you can't switch the radio station. I'm not too good with cars, so could you help me? Does anyone know what I could do to get my stereo to work?