Mystery solved. The buck boost ground wire is connected to the house system negative bus bar, and it turns out that is not grounded to the chassis, so the loop from the starter battery to the buck boost is incomplete. Using a long test lead I connected the buck boost ground terminal to the starter battery negative terminal and I get a good reading of 12.4V on the TSConfig software.
Now, I just have to figure out how to ground the negative bus bar to the chassis…
thanks
td