X1 won't calibrate gimbal pitch

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I hope someone can help with this. I bought a gimbal, agptek brand. I wired it up the phantom controller, using the F2 slot for pitch control. I am able to set the "center" value, and can see the gimbal react on the bench. I installed the plastic lever on the back of the transmitter, and I am confident it is intact. My problem is this: I am unable to calibrate the X1/stick monitor calibration. The slider marker turns red, and does not move. So I am unable to control pitch. I am running the latest software, with gimbal control. Am I missing something? Is there a patch somewhere I have to enable? As expected, the gimbal came with no instructions. Is there a chance I have it wired wrong into the controller? I have been working on this for a while, and I am running out of ideas. Any help sincerely appreciated.