My son has a Bontrager Duo Trap that he uses with a Edge 1030 Plus and several other Garmin devices before the 1030+. He's never had an issue. I don't know if there is any info you can glean from the LED's or other stuff for troubleshooting, but I'll try to ask if he comes by.
It is hard to say what is at fault though. The Garmin or the Duo Trap. You might do a soft reset on your Edge just to make certain any updates got applied correctly and are in full effect. Maybe take an in depth look at how the 1030 shows the paring and be certain that it doesn't just see the Duo Trap as a cadence sensor only.
Are you sure you gave it enough time to register speed after spinning the wheel? Also, with some of the much earlier Garmin Edges, speed sensors were sometimes quirky for some when not moving as Garmin seemed to figure that if you were on a trainer in the house, you didn't need to know your speed. And I quite agree that on a trainer, speed is meaningless. But I think they've changed that. But since I don't use a Garmin device with a trainer, I don't really know.