Radio not working on 2006 Mercedes-Benz S430

After muting the radio, the sound wouldn't come back although the radio was not muted anymore. Everything looks normal on the screen, navigation works as well, but no tone. Any idea what might went wrong?

Asked by for the 2006 Mercedes-Benz S430
I am not familiar with Mercedes and don't know if this is a common stereo failure with your model of Mercedes. I would start by calling the dealer (or several dealers and ask them if they have seen this problem before. If they say yes its common requires pulling the stereo and getting it repaired, Google "original stereo equipment repair" load of places specialize in repairing factory OE stereos the link below even tell you how to remove the stereo.
The place we use to repair or stereos here in California the fellow tells me whats wrong with the stereo before I have even finished describing the problem if its a fault they have seen before.