I found the same thing on my Crusader between the LR and the BR. What I found, was some of the coax insulation was still covering the coax conductor in the connection going into the wall in the LR coax. Therefore, almost none of the signal was getting to the TV. As soon as I scraped that away, that TV went from 6 channels to 38.
Check your coax connections.
Ben and Doreen
Home Away From Home - 2017 PT Crusader 315RST
TV - 2008 F250 Lariat 4X4 6.4 Diesel
42 nights camping in 2015
61 nights in 2016 (still not enough!)