Just to update the world on this, we got it resolved by adjusting the double latch bracket with the original bracket as high as possible (with the latch closed to relieve tension) and the Hansshow bracket as low as possible, then releasing the latch, which caused the problem that it wouldn’t close because the tension on the emergency latch was too tight.
Once that was done it was smooth sailing.
If the instructions in any way conveyed these possibilities, this entire install would have been so simple.
Also the Hansshow customer service, while they tried, just absolutely sucked. They assigned me an engineer who kept just randomly suggesting the dumbest things, like telling me to switch a wiring harness to the other side of the car where there was nothing to connect it to. This should’ve been an easy fix for them and I feel like they made it 20x harder.