Mike,
Normally the AC / heatpump only puts air through the duct work in the ceiling. The duct work in the floor supplies heat from the gas furnace.
Certainly I haven't seen all makes and model RVs, but I've looked at a lot of them and just haven't seen one that had ducting connected to both the floor and ceiling from one unit.
If you have one that does and you are getting air only from the ceiling, the heatpump is working and you have an obstruction in the duct going to the floor.
Follow your duct work to see where it goes to the floor.
