I have a 2009 a4 avant s line with the Audi concert system, everything has been working as it should do since owning the car for the last 1.5 years, was casually driving whilst listening to a cd 1 day when the cd suddenly stopped playing, I ejected the cd thinking something was wrong with the disc and then inserted it back in but nothing, I've googled many times and even been into Audi who were baffled, of course they were willing to book it in and have a look for a fee!
I've had a fiddle myself and all I can tell you is that it tells me the external aux is active and also that the disc is unreadable, the radio works fine so do all the steering wheel controls, I'm assuming I must of touched something but what I just can't figure it out nor can I get my CD player to work again!
I have also tried to do the resetting thing but my unit doesn't seem to go green when holding certain buttons so maybe my unit has developed a fault?
So hoping that someone out there can help me put an end to this puzzling problem of mine!