2017 Jayco 31FS cable/hdtv hookup help

Usually, when on cable, you want to turn off the antenna system. Most often a button with a light on a wall plate inside one of the over-cab cabinets (I think the 'boost button' you are speaking of). Both the antenna and cable signal enter the TV through the same threaded coax fitting (why the booster button must be off). Once you have the campground cable connected to the proper place on the RV, you will need to go into the setup function on the TV and select 'TV' in the list of inputs (expect to see HDMI 1, HDMI 2, TV (sometimes antenna), USB 1, USB 2, AV1, etc. if you are looking in the right place. Some remotes will have a dedicated 'input' button. After that, you will have to let the TV do a channel search. That should let you select between antenna or cable before the search begins. I'm pretty certain your issue is with the TV, not the coach, check the TV manual. All the TVs in the coach should be wired in parallel to the same cable/antenna input and the procedure I mentioned needs to be done on each set if you want to watch on that TV.