R172 SLK250 CDi - 6 CD Changer issue

[MustangGT]

Hi, I am hoping the mega-brain that is PH can help me. I have a 2013 SLK 250CDi with the Audio 20 sound system. This morning the CD player appears to have jammed and is giving me the audio unit unavailable message.

I have tried a reset using the power button/clear button combo, and also tried remove/replace fuses 11, 16 & 26 which the handbook says is the COMAND system. No joy at all. It still plays the radio and also the USB (which appears as disc 7).

Any ideas gratefully accepted.

Many thanks.