In car entertainment issues
 

Hi everyone,
I have a Mercedes s55 amg 2000 model and I've lost all sound from my Bose in car entertainment system.
The problem started as an intermittent one where sometimes all the audio options would work with volume..i.e audio,cd nav etc but now I've lost all the volume and when I select the cd option it's telling me that there's no cd changer.
Can anyone help me with this?
I don't know where to start so any help would be greatly appreciated!!
Many thanks
Scott