Here's what I'd do - take the fixture, without the extenstion, and plug it straight in to the wall with an
adapter. Make sure that you don't have other high-consumption devices on the electrical
circuit that you're testing the fixture on. if that works, cool, your problem is somewhere in the cable or the
dimmer pack. So take the cable and now put the cable between the fixture and the wall adapter (all of this is assuming that you have a properly wired, working edison adapter), and if the fixture still works, you know that the problem is in the dimmer pack or the data run. If the fixture doesn't work when you plug it in to the wall for the first time, you have a bad fixture, but if it works the first time but then doesn't work with the extension, it's the extension.
Hope that helps.