No Sound From Center or Lower Door Speaker...SOS

(2004 V70R) There seems to be no sound coming from the center speaker or lower passenger door speaker. I'm hoping that someone has seen this before and would be willing to point me in the right direction for a fix. Is this a HU-803 issue or maybe as simple as a wire/fuse? Don't know if it's related, but the volume knob does not work. Spinning it in either direction does not affect the volume. Thank goodness for the steering wheel controls.

Thanks...