Oh, yes, the TV
As I have gone through many hours of trying to get this all figured out, I will offer some thoughts......
First, booster off when on cable as you have done. Make certain the cable feed actually is working....like if possible hook your input to another cable feed from someone else's site.
Check the source button on the TV and make certain it is correct....try them all if unsure.
Make certain your cable connection is to the cable female connection on the trailer exterior and not on the satellite input. If this does not work, try the other connection as it may have been wired improperly at JC.
To get the Television off the mount, look behind and you should see an "L" shaped silver colored piece about an inch long, attached near the top of the bracket by a small bolt/screw. Loosen this and rotate the "L" bracket to one side and the television should fall forward....have another person hold the television to avoid it falling over and breaking. Once this falls forward a couple inches it should lift out of the bracket.
Check all the connections before replacing and reinstalling the "L" piece. Incidentally, the "L" piece cannot be installed after placing the set into the bracket, one has to have it up, loose and rotated to one side, then replace the set.
Also, sometimes the cables are not well connected so, I usually spray a bit of electrical contact cleaner/lubricant on the connections and reconnect them.
Happy trails and Good Luck
Ms Tommie Fantine Lauer, Greensboro, NC
AIR #31871 WBCCI #4165 K4MTL