I have had this problem a few times. The easiest fix was finding the gcfi that was tripped and resetting that. Some of the outlets are fed from those so if they are tripped the outlets being fed will also be off. Another time it was the wires in the back of the outlet just came loose. Be careful taking these off since they dont always go back in easy. some are cheaply mounted so can be a pain to mount flush again. The worst one was on a pup I restored and the wires were chewed by mice. That was just a trial and error on finding the bad section and running new wire.
REMEMBER ... shut off shore power as that can really hurt.
good luck!