Did you make sure the roof antenna power was switched off? That also switches the TV connection to the cable input. The TV does need to do a channel scan of course.
Dutch
2001 GBM Landau 34' Class A
F53 chassis, Triton V10, TST TPMS
Bigfoot Automatic Leveling System
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox baseplate