I have assembled my first mechanical keyboard using the xd75re PCB. I used a plate mount, and all of the switches were installed without issue (this PCB has hotswap). When I used keyboardtester.com to test the keys (after assembly), I found that there was one key that wasn't registering at all (from the factory, it was the letter 'D' in a qwerty layout).
I tried the switch in other locations and it worked. I also shorted the contacts for the key using a paperclip, and it registered the letter ('D'). Yet, when I put the switch (or any other switch) into that location, nothing registers.
I thought that the pcb might not be close enough to the plate for the switch to reach the contacts, but all the keys around it work and the plate is parallel to the PCB. Tightening the closest bolts made no difference holding the two together did not make the switch work either.
I'm at a complete loss for what to check next. Everything else about the PCB and the switches work perfectly. I am able to type on the rest of the keyboard and was able to flash the microcontroller without an issue.
Any help is appreciated.
UPDATE: None of the switches were properly seated (from inexperience generally and with hotswap in particular), which caused the plate to bend away from the PCB. After testing again, with the plate and PCB parallel and all the switches flush, the 'D' key still does not work. I've re-checked the switch and the PCB, both work separately.