Do you have another outlet in the house that you can reach that may be on a different GFCI circuit or not on a GFCI circuit? I would also use a meter and check for a short in the connections on the side of the camper. Check for a junction box under the camper between the side connector and the breaker. If there is one, take the cover off and make sure there is no water in it.
2013 Silverado 2500HD LTZ CC 6.6L Duramax Diesel
2014 Sunset Trail SF270BH
Holly & Buster, mini Dachshunds
2016: 1 trip, 3 nights in 1 state, 316 miles
2015: 5 trips, 18 nights in 3 states, 2707 miles
2014: 5 trips, 14 nights in 3 states, 2426 miles