The converter box is only for receiving digital over the air broadcasts on a TV with an analog antenna tuner. They have nothing to do with cable TV reception. If your TV isn't pulling in the cable TV either your TV is defective or you need a cable box from the front office.
That said in my camper when it was new I had to reterminate most of the cable TV connectors to get park cable to work reliably. To rule out your campers wiring you should run a coax straight from the pole I'm through a window to the TV. If that works you know your issue is in your wiring.