Presume you have tried this in several campgrounds so you know that it is not a problem with the RV park delivering the signal to your site?
If so, then maybe take your telly outside and connect with a new cable directly to the campground jack and see if it works.
If no, then the issue would seem to be within your tv - maybe you just need to run the channel setup program within the tv? We do this each time we set up and a new RV park.
If it does work when you connect directly to the jack on the camp ground post, then that would seem to indicate that you have a problem within your RV wiring.
I believe you did confirm that you have turned off the antenna booster. With our trailer, the cable does not function if, in error, you leave the booster switch on. I think you know that!
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.