the ground-fault breaker where? in the trailer itself, or at the supply outlet where you're permanently parked and connect the trailer?
your battery charge controller runs off 110VAC. find the outlet your charge controller is plugged into, and test it for line voltage??
if you have no power at that outlet, then it's likely a 110VAC problem, and work back toward the supply.
if you do have power to the outlet, then it's likely the charge controller, and it could be time for a new one.
we use an Iota DLS55/IQ4 that's generally worked well, but there are other brands and models available.
Joseph & Gabrielle
Simplicity is the ultimate sophistication - Leonardo da Vinci.
WBCCI 2087 - AIR 3144 - TAC-NJ2