On a lot of these systems the coax feed from the selector box to the rear of the coach , is split to the bedroom and the basement . The system you have may have a splitter, or even cable ( RG-59) that is not rated for satelite. If you are hooked to park cable does the bedroom TV work.
If the carry out dome has a second hook up it would require a second reciever, and related wiring.
I have no trouble getting sat signal every where in my coach,at the same time, all the same channel of course, but it came with RG-6 the sat rated cable.
I don't have Dish , but I've never heard of a solo reciever.Any thing in your manual?
Have you tried , switching the feeds on the back of the cable selector box, so that the 2nd TV output would feed the main TV, just to make sure the selector is working.