Suspects in order: Park power,, including the breaker but I have seen neighborhood blackouts, one involved JUST the park, some a good chunk of area,, Reason I put a transfer switch in house, Reason a friend of mine put in an emergency generator... She posted this AM that it kept her house comfortable last night (She is in New Orleans) when power failed for her neighbors.. SHE still had power, She made her own. 20KW Koheler.
Cord, epically the plug end
Auto Transfer Switch (The switch box)
These come in two types. ONE looks for power on shore leads and if present connects,,, That is kind of complex by my standards.
They BOTH look for generator power, and connect to generator if present (Mine only looks for Generator,, No generator it defaults to shore power).
IF you are comfortable working around 120vac.. Open this box.. Find the terminals where SHORE power comes in and either hook up a TEST lamp or use your volt meter to see if power is arriving,,, If it is, then check the LOAD terminals,, IF power is coming in, but not out, your problem is the switch.
If not coming in it's the park or the cord, Measure at the park (I am assumign your neighbors have power)
I have had the box where I plug in fail... Three times.