New 3DS XL C-Stick and ZL/ZR not working

Hi guys, I’m fixing a n3DSXL and am almost finished (previous owner bent a bunch of connectors, so I either bent them back into shape or soldered new ones in place). The only issue that is left, is that the C-Stick and ZL/ZR are completely non-functional.

Everything else works fine and I know the C-Stick and the shoulder buttons work fine in another 3DS (I also swapped over the power/button PCB and ribbon cable).

I’ve also had this same issue with a n3DS (non-XL), but wasn’t able to fix it and ended up swapping the motherboard. Does anyone know what the issue might be?