The refrigerator works on 12 volts. If you have 120 VAC coming into the trailer, there is no guarantee that the 12 volt
DC to the appliance will be working. Check the power supply that charges the batteries and supplies 12 to the trailer. Start by checking for 12 volts at the batteries and then work backward through the fuses to the refrigerator and at the input to refrigerator it self. Do the 12 volt
lights in the trailer work? Is there a proper ground to the batteries? there is a fuse on that ground as well.