I don't know the specific system you're referring to, but just a question & a general suggestion:
1) Ok, I know this is the obvious question but... any chance you could have just accidentally changed the input/output settings on the audio head unit? I did that on the audio system in my Voltage one day, and it about drove me nuts trying to figure it out. And, it didn't help that, after I made any changes, the system had about a 10-to-15 second delay before it takes effect!
What I mean is that I'd switch audio output... hear nothing... and change to a different setting. Then, by accident, I happened to leave it on the setting I thought should be the correct one while I went to get the manual yet again... and about 15 seconds later, WHA-LAH!! All of the sudden I had surround sound in the rig again. So I was putting it on the correct setting after all.. but I wasn't giving the system enough time to make it's internal switches.
2) You say you've taken the unit out and checked things. Did you connect a different set of speakers to it to see if they would play? Maybe you've got a pair of old car speakers, ,or an some stereo/home theater speakers in your house you could use to test with? If the different speakers play, you'll know it's not your audio head.
2013 VOLTAGE 3200 (EPIC I & II)
2014 Ford F-450 PLATINUM