Tom and Lisa - wow. Had a very similar problem (I really believe it is the exact problem) with our 2015 Challenger 37TB last month. If you are charging with Shore and Generator power but not with the automotive alternator - it is probably the Trombetta relay/solenoid. Check out the info at the post below. I put up pics, wiring diagrams and lots of other folks contributed (to include Thor Warranty Service). In a few words, the Trombetta relay/solenoid - working with the BIRD - closes after about 30 seconds allowing engine alternator current to pass through and charge the house batteries. If the Trombetta relay/solenoid doesn't close, no current through to the batteries. The Trombetta (see the pics to see what it looks like) is located at the back of the house battery compartment on the mounted with 2 screws. The BIRD (again see the pics) is about 6" to the right and on the back side of the same metal frame work.
http://www.thorforums.com/forums/f8/...sue-10928.html
I am also including a link to an Ebay seller for a Trombetta relay. I tried to buy one off Amazon and I wound up at Ebay (Amazon kept sending a intermittent vs continuous relay). I don't like buying at Ebay but this seller was fast and less expensive than anywhere else.
https://www.ebay.com/itm/NEW-TROMBET...53.m2749.l2649
Hope this helps.