I do not know how, but I lost all 12V in coach. I have 12v when the gen is running but if I turn off gen the 12V is off. I can not locate master switch - if any.
To get a good answer, give a little information about your RV. There might be someone on here with the same year/brand/model that's already run into your problem and fixed it.
You may have what's called a "salesman's switch" next to your entry door. It's meant to reduce the battery drain of RVs while they're on display.