The plug was wired wrong; fortunately I have spare GH1.25 housings and experience with building those plugs so I pulled all of the pins out of the plug in my image, reversed the order, and plugged it back it and now it works. So it was definitely sent out defective; also, it’s obvious that it wasn’t tested before being shipped to me, since it would clearly not have worked in that configuration. It might be a good idea to test these things before sending them out, considering the cost. However, all’s well that ends well–it seems that neither the sirius unit nor my FC were harmed by the incorrect wiring.
Definitely pass the message along to your assembly people to keep an eye on that–it is honestly an easy mistake to make (I’ve wired my share of plugs backwards) but it could be a costly one.