[JRTJH]

If you've set up the TV's correctly, then I'd run the campground cable to the outside TV (easier to access and route the cable) and with the direct connection, rescan and see if you have any reception. If you do, then it's in the trailer "somewhere"... If you don't, it's not your trailer but the campground cable distribution system......

I see you've already commented that you did the above... So, next step is verifying the cable from the rear of the trailer to the booster. You know the from the booster to the TV's is working because you have OTA reception over those same cables. It's somewhere between the back of the trailer and the booster connection.