When I got my 2015 GLA45 I had no sound on any input except the sat(sirius)
I checked everything (fuse/optical loop...) and plugged it back and it Worked for a bit and went off again when I put back in the unit completely. So my first guess was a lose wiring but all seems good on this side.
I checked the diagnostic and got 2 error on the ground of the antenna. If anyone knows where to check or troubleshoot those ground. I checked in the rear and cannot find them. Is it part of the windshield since it has been changed recently?