Can someone help me troubleshoot why my 6-Y-H-N row is not registering?
This definitely sounds like an issue with the MCU (at least from my experience). I had a similar issue on a different build where one of the rows on my PCB was not firing (I think it was F8-0-P-:). I'll detail the steps I took to fix the issue (see below), although it's a bit risky and I'd try to see if you can source a new PCB if possible.
Basically, it seems like there is a spotty connection from the 6-Y-H-N column to the MCU. In order to fix it, you have to identify the pin on the MCU that corresponds to that column. I forget which MCU is used on the Gotchic70 (maybe ATmega32a?). If so, Google "atmega32a pin out" to find an image with a list of the pinouts for the MCU.
Once you've identified which pin corresponds to the 6-Y-H-N column (unfortunately, I'm not at all well-versed in these things, so someone else might be able to help you with that), you need to re-flow some solder to that exact pin. Your best bet is probably to use a flux pen to apply some flux to solder.
I should warn you to be very careful when you solder the pin, and to only solder the exact pin you need. From my personal experience on a different build: I ended up accidentally soldering a few pins together on the MCU (used soldering wire instead of flux, don't do this), which caused half the columns on my PCB to stop firing. Wasn't able to remove/revert my soldering mistake = PCB ded.
Also, I think Nathan encountered the same issue during one of his builds. You can see what he does to troubleshoot the issue here (starts fix at around 2:11:50):
Not sure how helpful this is but good luck!
