check fuse in plug tip... if "brains" appear to be working working and you confirmed power at plug, this likely is your culprit.
FYI, they always suggest "plugging" in car first and then charger.
And by sounds of it, you have the Porsche Charge-o-matic II which is a rebranded C-Tek multi 3600 or some such. If you also have the direct connect or "alligator" clips, try those as well to further isolate issue to cig lighter plug.
Good luck
