It helps to give some information about your RV like the make, model, year. Also the type of 120V system you have, as in this case. Does the load center have a name? How many breakers are in it?
First things to check--Shore cord function, load center wiring (are all wires tight into the neutral lug bar and on the breakers?), ground continuity to frame. If you have a non-functioning GFCI receptacle, pull it and check for power at the terminals. If you have power there, the GFCI has failed or there is a bad device tripping it in that circuit.
Do you have a hand-held meter?
