quest distribution center

I have a quest distribution center as many motor homes have. I have all TV's connected to it. It works fine but I can't get digital channels with cable on my tv when running though it. I can however get digital channels with the antenna. I have tried all outputs and get the same results. I can take the main input from the cable coming into the coach and connect to the tv and get digital channels. Hook it back up to the quest distribution center and no digital channels. I went to camping world and purchased a new quest distribution center and it did the same thing. HELP!!!