Hello. Try unplugging everything that is plugged into that circuit and see if that clears the light. Sometimes an appliance can be mis-wired and cause the reverse polarity light to come on. Are you plugged into your normal dock? Any electrical work done recently?

Strange. It could actually be that the circuit that detects reversed polarity has failed for some reason. What you might want to do is double check - most hardware stores, Home Depot, etc. sell a small circuit tester for less than $10 that you can plug into any outlet and has LEDs to display wiring problems. I would use one of these to verify what your light is saying - I suspect you may find that the circuit tests out fine. BTW, the circuit tester is a handy thing to have anyway - you would be surprised how often home outlets are wired backwards, and that can be dangerous.

OK, you didn't mention that the circuit didn't work now. That makes it a somewhat different problem. I am assuming you have a single shore power cable for both circuits, and the A/C circuit is OK, so we can eliminate the shore power and cable. Somewhere in your circuit - probably on the outlet closest to your circuit box - you probably have a GFI. If you have not already, check the GFI to make sure it hasn't tripped (there will be a "Reset" button on it, along with a "Test" button). Usually the GFI is on the first outlet so it can protect the entire chain. There may also be a regular circuit breaker for that circuit, but I would expect that on the panel and assume you would have checked it. If not a GFI fault, you will need to use a voltmeter to trace the AC voltage from shore power onward until you find where it disappears.

OK, then you really need to start checking power all the way back to the dockside outlet. There should be a breaker on that, so that could be tripped. Also double-check that your shore power cable is firmly connected at both ends.