The running lights/brake, etc are straight from the TV. But are juntioned in the tongue area lift pump/battetry box.
The electric plug ins, 120v, are protected by circuit breakers in a junction box inside of the trlr. There should be 3-4 that control all 120v. AC has its own 120v breaker. Refrig has its own breaker. The 120v> 12v converter has its own breaker.
There is also a GFCI in the trlr that can trip and make all of the plug ins NOT work. Make sure it is reset by pushing the button.
All interior lights, and porch, are 12v, fan is 12v. These run from the 120v converter. The converter also has 12v fuses on the inside of the cover for the 12v items it controls.
My 120v circuit breaker box is in the cabinet to one side of the refrig. The converter junction box is in a cabinet on the other side of the frig.
Once you have identified the locations and that current, 120v or 12v, are good at the breaker/fused location then you know that any non-function is down stream from that source. A multi-meter is your friend and should accompany you on trips at all times.
This is how my trlr is laid out, your will most likely be slightly different but similar.
If you have specific issues don't hesitate to ask for assistance
2002 ford f350, 7.3 diesel
1985 hi-lo funchaser