Typically there are a couple fuses on the main circuit board. It is accessed from outside - take the access panel off and in there near the bottom is a removable cover for the board.
Usually one screw and a couple clips to fight with to get the cover off. Fuses are on the circuit board.
Did you check for 12V at the fridge, in the access compartment? Nothing will light up or work without 12V.
There is a 12V feed to the connections at the bottom. Usually a junction block in there with a screw connection. Probe that with a test probe to see if 12V is there.
If 12V is there at the back and onboard fuses are ok, it is possible that the main circuit board is dead. Hopefully not, as they sure don't give those away! I lost one on the road a few years back. Dealer soaked me 250 bucks for a stinkin little circuit board. But it was a Dinosaur Board, the best repalcement brand out there.