RoyB just created a new High Water Mark in explaining and posting info about that Winegard "plate..." What it Is, Does, and how it's Wired.
Has your TV setup always been like this, or has the situation changed recently?
Any recent work done on it?
You say "fuse on it" --- Where?
Please note that the "ON" mode is ONLY for OTA (Off the Air aka Antenna) reception. It makes "Park" or "Cable" picture SNOWY.
Our coach's TV cabling was seriously cobbed by previous owners so the two of them could watch different programs using separate satellite receivers. Holes through the outside walls (and not sealed!) plus extra cable along inside walls and the connections on the back of that "Plate" rearranged.
I had just unscrambled a TV cabling mess created on a Winnebago VIEW by a "professional" using Winnie's on line wiring diagrams and help from a very sharp coach owner. Figured I could surely clean ours up after all that. Dug out the diagram RoyB served out so beautifully above, and went after it. Done in an hour.
Be sure the "plate" has power, light up on OTA (ON) mode.
Go up and disconnect coax cable at antenna head. Should have 12VDC up there. If No, replace Plate. If Yes, the electronics in the antenna head could be shot.
Your antenna cabling can be tested for continuity. Disconnect both ends. Short one end, jacket to core. Then read the other end, jacket to core. Should be Short, Zero Ohms.
RoyB's right about the Radio, too. It seems you have a Trailer, so there should be a separate antenna. Hard to see in his pic, but the indoor end simply pushes into place in its connections. You may have to work your way to the back of the radio to check this. Be sure any extenders/adapters that have been used, are also plugged tight.