1. You state running direct to the TV cable works
2. The most common LACK of cable in the list below
1. Input to RV, you usually have Cable and a SAT input. THOSE are reversed. Connect the Cable to the SAT input and see if it works
2. You have 3 coax inputs on the back of the TV ant Booster. Ant/2nd TV/CABLE. If you have 2 or more TV's and all the TV's receive OTA roof top antenna reception, then the coax behind the booster is correct. IF you do not receive OTA on all TV's the odds are the 2nd TV and Cable coax are reversed.
3. You have a few coax plates at your main entertainment panel. You have 2 or more coax wall plates. Some for a roof top Sat/ some for that outside cable/SAT input. They wired the cable coax to one of those plates and NOT to the Booster Cable input. Doug