Sounds like your camper power switch (house power) is off. These switches activate a solenoid (you should hear it click) that allows 12vdc from the battery to come into the camper (house). The switch is often located near the entry step, door, or sometimes in the galley area, like on wall near the stove. If you can't find that house power switch, you're going to have to call the manufacturer or trace the red & black wires back yourself.
Do you have a multimeter? Check your battery volts after being off shore power for an hour...