I don't know that Jensen - but on your two questions:
1. You may find a two position switch on the dashboard or console below the radio that says. "Engine" and "Home" or house. This switches the radio between key on operation and house power. I don't know the exact wording it would say.
2. I have a totally different entertainment system and my RV came new from the factory with this exact same problem. It turned out they forgot to install a microphone. And, even if they didn't forget on yours, maybe it has become unplugged???
Lastly, on a related topic SOME models of WBGO motorhomes have a solenoid that will send charging power to the chassis battery when the house batteries are nearly fully charged. But some do not.
If you find that your chassis battery seems to keep doing down in charge when you are camped and on shore power then you may not have this solenoid - or it could have failed.
Many WBGO owners that do not have this feature install a device called Trick-L-Start or Amp-L-Start. This inexpensive, easy to install device bleeds off a little bit of power from the house batteries when they are charging to trickle charge the chassis battery.
2017 Winnebago Adventurer 37F
2016 Lincoln MKX Toad