I looked at a video on You Tube and it does look as though you only have one duct in the living area. It does sound like it is unhooked. I know it is a long ways to drive ; so call them first and set up a appointment ; but, it sounds like you may have to go back to the dealer.
In the mean time. You have had a lot of people telling you how to run additional electric cords to run a electric space heater. But, in my TT I just plug the heater into a normal outlet. I am careful not to run other high electric draw items at the same time as the heater is plugged in.( Don't tun the Microwave at the same time for example.) But, as long as I only run some lights, the TV, and the heater then I have never had a breaker flip while running a electric heater.