Originally Posted by ependydad
I would think another option is to bypass the motorhome's wiring entirely - run a cable through a door, window or slide and see if it works that way.
What he says! Do you have enough cable slack from the connection for camp plug to trailer outside plug that you could take it loose from the trailer, run it through a window or door straight to the cable box? I'd want to by pass all the other stuff and go straight to cable box then to TV to make sure everything works.
You said the cable company sent a "Ping" to the cable box, did they confirm they can see the box? If so then maybe you just need to run a cable out of the box straight to your TV if that works then you at least you have narrowed down between 2 points where your problem is.