MichaelB welcome to irv2 and your ever present Newmar forum.
How old are your house batteries.
Your House batteries maybe your problem.
You need to check also the ground for them on frame of your chassis. Maybe loose connection or corroded. Clean and reconnect with a star washer.
I assume when you checked fuses, also under panel on dash board deck.
You also have grounds on chassis frame for GEN and your steps.
Ground is common to every working voltage item in your coach.
As a free gift I'm giving you some ID as a member of this forum KARMA. Just below that entry you will see a signature block to input your coach and chassis info.
Let us know how your making out so we can follow up.
Enjoy all the forums on irv2 and post often.