Sorry GypsyYears, this thread seems to have gotten hijacked and sidetracked.
For the original poster, keep it simple, you just ran your batteries dead.......
1. Check the water in your batteries. If low, add distilled
water. If you don't know how full to fill, ask someone. Do not overfill !
2. Find someplace to plug the motorhome in for at least 24 hours, preferably longer.
3. Use a multimeter (or pull by an Autozone or other parts store) to check the voltage and test the old batteries. Compare the reading on your engine battery to the house batteries. If they are not about the same, you either have bad batteries or a bad converter.
Don't go out and start buying a bunch of parts to throw at it until you have some idea of the problem. Since you originally had a functioning system, and ran the batteries dead due to whatever all you had on that was draining them, it's probably just a problem with dead batteries. As dead as they are, they will not "pick up" a charge right away, hence the 24+ hr charging recommendation.
Once you do 1-3 above, get back to us and report the results. Good Luck!