Radio problem
 

I have a 2002 slk 320 I can't get sound to play. Radio lights up can change stations. When I switch to 6 cd changer it say no cd connection. I have power to radio and cd it will eject cartridge. I've disconnected battery and reset code on radio. I've taken radio out and disconnected all cables and power and reconnected. I've checked all fuses also I can hear click on amp when turn on radio. I'm stumped. Any suggestions? Thanks

Any codes come up off the DTC?