Has anyone encountered this problem and what did you do to resolve it?

Furrion TV is connected to Furrion sound system. According to Furrion owner's manual, to play sound through the sound system, instead of the TV's speakers, you must turn the volume all the way down on the TV, turn the sound system on and control the sound through the sound system. OK so far. The problem I seem to be having is that the sound on the Furrion sound system is too loud at a level setting of 01 and it doesn't change at all, no matter what setting I use on the sound system. It can be 01 or 10 and the sound level is the same. The only control I seem to have is that when it is set to 00, the sound goes off. So, I either have one setting that is too loud for us at 01 or it is off. Does anyone have any suggestions? I looked at the documentation from Furrion and there is absolutely nothing in the documentation about how or who to contact with the manufacturer.