iPod - no audio??

I have a 2010 RES/Tech and have been playing my iPod through the USB connection in the center console. Had this car since last year and had been playing through the same source ( USB) since. Always reliable and never skipped, issues etc.
Had a B13 service couple days ago at the dealer. Got it back and still played normal. No issues.
Today, got in the car and lo and behold, no sound??!?!? The screen shows the usual display i.e. track titles, singer, genre, etc. Display is completely normal but totally no sound/audio... :whyme:
Tried the same USB cable on my iPhone and same thing.. no sound. So, I changed the cable ( thinking it might be just a bad cable) to a spare one and same result. No sound. Display on screen shows the everything, .. title, singer, genre etc but just no sound.
No choice but to plug in through the AUX source. Sound came back and everything was normal but of course, with AUX, I cannot control the songs, change songs etc with the steering wheel controls... this is exasperating. I was wondering if I accidentally hit a "mute" button somewhere that I do not know? Maybe?.. Tried most everything from pressing all relevant buttons to shutting off engine and re-starting. No avail. :annoyed:

Anyone know of anything similar or experienced the same issues before? Please help!!!!!!!!
Thanks