This has happened to me a few times as well, no sound. I reset the radio by holding the power button down for a few seconds, this allows the screen to reboot. Worked both times.
I'd had the issues with the speakers cutting out. The turn off/turn on fixed it for a few times. Eventually I only had sound coming out of right rear door. I was told by dealership that right rear speaker is directly wired, while the other speakers run through an equalizer. They are replacing the equalizer (that's on back order) now. I hope that fixes it.
