To be a little more precise, and assuming you have a rear bath model:
Get on your knees in front of the streetside closet between the bath and the sleeping area, closet door open. A flashlight will be useful here.
Stick your head in the closet, and look at the wall at the floor of the right side of the closet. That blue metal door hides the fuse panel, which is the front part of the Univolt (the device that takes 120V and gives you 12V).
Check the fuses, "just in case", but if the trailer is plugged to 120V and you don't hear the buzzy hum of the Univolt, highly likely it's dead.
When you replace it, be sure to get one of the modern ones that has three stages of charging; your battery will last longer.
Good luck, and looking forward to hearing how you make out!