Old 3DR Pixhawk 1: "Detected 0 radio channels"

Hi, I have an old 3DR Pixhawk 1 (from ~2015 or so) that I am trying to get working again. I have it plugged in and communicating with QGroundControl no problem. I have upgraded the firmware to PX4 v1.11 and have been able to complete a lot of the setup & calibration steps for the gyros, accelerometers, etc. However, I am not able to get the Pixhawk to see my radio receiver.

I am using a (relatively old) Spektrum DX7 paired with a new AR8010T Spektrum receiver, and I have confirmed the radio and receiver are communicating correctly with an independent test (unplugged from the Pixhawk). Then, when I plug the small satellite receiver into the SPKT / DSM port on the Pixhawk and hit the radio “Calibrate” button in QGC, I get the error “Detected 0 radio channels. To operate PX4, you need at least 5 channels”.

I have tried the solution outlined here with no luck:

I was wondering if anyone had advice on how to fix this issue. Considering the age of the hardware, it seems like everything else is working surprisingly well, and this is the last thing holding me up. Let me know if anything is unclear…. I am new to this work so I may have missed something obvious. Thanks!