As Larry said, make sure you have 12v power to the upper right connector (viewed from the rear) when your motor home key is on. The Mopar harness requires 12v from the towing vehicle for it to work. I had to run a 12v line on my Itasca, but the new Tiffin came pre-wired with the hot wire. See the below diagram for standard RV wiring.
Dan & Ro with two Rescued Boston "Terrorists"
2015 Tiffin Allegro RED 38QRA
Previously '06 Itasca Sunrise 35A on a W22 Workhorse
'12 Jeep Wrangler Sport and/or '08 Honda Goldwing