I have an Open Range, Mesa Ridge 345 and had the same problem.
Even when a new cable was installed I had no luck. Tim at Open Range in Ocala picked up a connection at the back of the rig and installed an input box at that location. Dish reception is great now.
Am pissed with Dish, however. We have a Tailgater + VIP211z receiver and want to use their Hopper recorder. Hopper will not work w the 211z. The Tailgater+VIP211K+Hopper will work together but Dish tells me they will not permit the hopper to be used in an RV.
It's times like theses I wish I was a Lawyer...
Good luck