tv receptacle problem

It appears that I don't know enough to ask an understandable question. For that, I am sorry, and I do appreciate your patience. First, let me start with all your suggestions: As far as fuses, I have checked all fuses and breakers in the panel. (as far as the push in 12 volt fuses, they all look good but I changed the one for the tv receptacle anyway. Still dead. Could there be an in line fuse somewhere? Wires in receptacle box appear to be secure. This unit only has one GFI test/reset button & it's in the bathroom. There is one more connected to the GFI inside and two more in storage compartments outside. All were checked with a tester and all showed hot. Don't believe this is problem. When I referred to the receptacle as 110 and 12 volt capable, I may have confused everything. I believe I read somewhere that if I wasn't hooked to 110 AC I could play the TV off the battery thru the same receptacle if the ignition was off. However I can't find that now so I may have dreamed it (Hell, I'm old). That may be true IF I have the inverter ON. (Help me out here). One thing that confuses me further is there is a small match box size gizmo sealed to the back of the otherwise ordinary receptacle. It's not a cigar lighter type, it's just an ordinary looking receptacle except as noted. I have no power of any kind to this receptacle & this is a dedicated TV receptacle. I have been hooked up to shore power through all my testing. Thanks again to all who replied. If you still don't understand try me again with any questions. Oh yes, I think my profile info was wrong on original post, I no longer have the 5th wheel, now it's a class C. Jack