Four eyes are better than two.
My daughter and son-in-law came up to visit today. I'd already told him about the problem. We took the volt/ohm meter out and started doing all the checks I'd done in the TT then he went out to the tongue and to the breaker on the frame. He took the cover off of the junction box that I'd used for a ground and after a bit he said, "What-t-t-t-? Someone at the factory or the RV dealership had taken the positive battery wire off the right side of the breaker and tucked it up underneath a large black cable out of sight. He said the end had never been on the breaker terminal screw. That was the problem.
We're suspecting that it was a factory error but for sure, the guys at the RV dealership never checked out the 12V system. They wanted the AC on.
So tomorrow I'm starting to install the solar system and inverter.
Thanks again to all who tried to figure the thing out.