My 2004 trailer has three GFCI receptacles. One near the sink area, one in the bath room area, and one at the bedroom sink area. These receptacles have push buttons on the center of them. You can see where one is tripped. The way the GCFI circuits are wired one tripped GFCI receptacle will cause several 120VAC receptacle to lose power down the leg.
This is what my 120VAC receptacles looks like that has GFCI push buttons on them
When plugged into home garage 20A 120VAC receptacles insure all three wire connections on the RV30A-15A Adapter are being made. The trailer requires all three wires being hooked up. (HOT-NEUTRAL-GROUND)
Roy Ken