In my experience with 12 volt systems, it's usually I who made the mistake(i,e. clipped a wire from the harness, blew a fuse , etc.) It's odd that when you crank the gen, your system works, though. Was it a good battery that you put in?
I've swapped sides , after having been a boater for 30 years........this is my first experience with rvs. I've always found 12 volt fairly simple and forgiving(and unless you're knee deep in water, holding a wire in your mouth, you prolly won't get zapped.)
I'd suggest there's a hot-side lead you may have missed, as it all works when run through the inverter.
I have a similar problem; but, mine is that exactly half of my interior lights work, and the aft half doesn't. They worked fine the day I wrote the check , though. I'm thinking this may be a fuse.
93' Fleetwood Flair
It's so new to me , it doesn't have a tag yet