Audible Illusions M3

Left volume controls both speakers on dual volume/balance knobs. Left control knob set to 0 and right side does not put out signal. No sound out of right speaker.
First few (less than 20) hrs played well aside from a little on the bright side with very little bottom. Noticed sound getting brighter and almost no bottom, like an am radio almost, but cleaner. Unit is pristine so I thought it was new and needed break in time. Powered up the next time and noticed a drop in volume with both speakers playing out of the left volume control.  Anyone have an idea what is going on and how to fix please. Just purchased unit with no history. Held in storage for many years.
Thanks