Can't get my entertainment center to work on Camp Cable

Most cable systems today have their own "digital box" and you don't even use the tuner in the TV. Didn't the campground give you a cable box?

I have a Cambria with the entertainment center. What I have found is the switch box that came with the unit is absolutely worthless. To access the rear, you must either remove the TV, which I have done numerous times or maybe remove one of the side speakers and stick your melon in there to get a look.
The moldings on my unit were fastened with square shaped bits and come off easy, the TV is then screwed to a metal frame after it is mounted onto another metal frame.

After struggling with some of the same issues you speak of, I use my roof mounted dish where I can, and if that doesn't work grab a book.

As you look at your tv there is a cabinet to the right. If you go along that cabinet all the way to the end and turn left, you can continue down that wall till you see the STOP sign , then hang a left to the locking release.
That's where the locking release 'might be'. If not, you will have to try to view some basic bracket styles used in rvs and try to find one that matches yours.
It has to have a locking release so you can lift up the tv to release it from the bracket to access your HDMI ports etc . See the link for vids.

http://www.tvformyrv.com/rv-tv-mounts-brackets/