Regular lamps work on AC, DC and reverse polarity DC
LED come in two types. ONE type.. see above
The other kind works
On DC
On ac but at reduced brilliance
But not on reverse polarity DC
Now bulbs come in a few flavors physically... Some you can turn the lamp 180 degrees and reverse the polarity (Wedge based) some you can remove the led assembly from the adapter and plug it in the other way around into the adapter. And some... Dissassemble the lamp fixture and odds are you will find a bunchy of white wires and black wires coming from the sockets to a common point.
IF this is a 3 light fixture the wires from the sockets should are most likely bundled WHITE, WHITE, BLACK and BLACK, BLACK, WHITE the one that is not working being the odd one... I suspect by now you have figured the problem.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times