So I can finally report a resolution to this problem.
I went out today and no power from the batteries. I looked at the wiring coming from the cables and saw a couple of small rubber boxes. Voila - they each contained a fuse. And one of the fuse had broken. Now, I graduated college with highest honors and am an educator - and don't think of myself as 'dim'. So - I immediately got on the web searching and calling auto parts stores to see where I could purchase an 'OE" fuse for a travel trailer. No one knew what I was talking about. So as I'm about to post on this forum for advice (would could have turned out dramatically embarrassing), I picked up the fuse to look at it and discovered, yep, you guess it, a '30' amp fuse, not an 'OE fuse.
Replaced the fuse and all is well.
I do have one more question: I've never really used the trailer just on batteries. Would it be helpful to the batteries to drain them down once in a while - or does that even matter.
Thanks!