Steve:
I know that should have been the first thing checked. I didn't, until I read your post. 3.8v on the chassis batteries, 11.8 on the house side.
The day before I had the macerator fail, I had turned on the ignition to fine tune the levelling and all was well. Now, when I turn on the ignition, I get nothing. So the chassis batteries are now on a separate 10 amp charger. Those are less than a year old, so hopefully this, their first deep discharge, will not kill them. Then I need to find out why, while plugged into shore power, with the inv/charger showing 11.8 and float, there was no charging happening.
I also connected to my car battery and all the stuff n the water bay works just fine.
Big thanks to Steve, Fred, Larry, Lee.