Sorry yeah you mentioned that in the first post.
re-reading, you have no DC power to the house with fully charged house batteries. But you do when you Aux it and or engine running which is supplying DC from the chassis either from the chassis batteries or engine alternator (or both).
I’d suggest tracing from house batteries to converter to the DC fuse panel in the house(coach). You may have let the smoke out of a wire or the converter and have a dead short between the batteries and the DC fuse panel.
could been from the large amp draw when you linked the house batteries to try to start the engine with dead chassis batteries.
it may help to draw a diagram, and knowing you maybe can’t physically inspect every wire due to where they are run thru the coach, you can check continuity at the ends and hopefully find a bad wire or?? And check the converter output. Coulda blown a fuse on it (I think they have fuses?)
Youll find it. Good news is it’s not some random thing as in you know when it happened and what caused it. So a bit easier to isolate I suppose.