Navion sat to long

I tried to get my Navion ready for a trip this weekend and discovered that the main starting battery had died. Put it on a charger and restarted the engine and it runs fine. Problem is that I can’t engage the transmission in drive or reverse. Displaying need service on the dash. Also a problem with the adaptive cruise control system. The Navion is a 2022 model with less than 5,000 miles on the odometer. I am new to RV ing and I guess I am learning the hard way.
I think it must be a computer problem so the plan is to disconnect the starter battery and let it sit for a while then reconnect and see if the computer will reboot. Towing it out of here would be tough. Mountain property with lots of trees overhead. Can’t see it loaded on a Flat bed.
Any one out there with possible suggestions or similar experience