I'm having a strange problem with a WD 15 I purchased with a Latitude 7285. When I connect the WD15 dock to power (i.e. plug it in to the outlet), the blue light on the male end of the power cable for the WD15 turns on, suggesting that power in flowing. However as soon as I plug the power cable into the WD15, the blue light turns off and the dock itself does not turn on.

I've tried multiple permutations of this including unplugging everything from the dock and connect power first, and multiple different power sources (including directly to the wall or to a APC surgery protector/battery backup) and always the same.

Am I missing something?