Since it all worked at the walk-through, you probably have a selection of input problem.
For the campground cable, the outside connection must NOT be on the SAT prep jack (if your RV has that). Then you pick TV from the TV on-screen input selection, search channels, and done.
For the DVD, select the HDMI from the TV on-screen input selection, activate the HDMI box and select the DVD input on the HDMI box.
Call TMC customer service or your dealer if these steps don't work: