Often two 120 outlets are put on the same GFI circuit. So that the one GFI will trigger if there is current on the other circuit. This may be the case in your boat. Certainly the plug near the galley must be GFI protected or the boat will not pass NMEA certification.
If you have a refigerator, there will be a separate 110 V plug for it--and it may be GFI protected also.
I added a fourth plug, with its own breaker. l This is on the top of the aft port cabinet for the microwave. I will add a second plug there for the microwave when running on the inverter, rather than using a switching inverter. (a 150 amp breaker will turn the inverter on or off at the power source).
Try tripping the GFI on the port plug and resetting--if the galley plug is still not working, take a digital volt meter, and put it on AC, and measure the voltage between all three points in the 110 V plug. It is then check to be sure it is properly wired--checking both at the switch pannel and the back of the socket under the dinette.
