On a used alt OP-1 I bought a few years back, there were a couple of keys not working, I tried a few things to resolve without success, ultimately I bought a replacement key bed which obviously fixed the issue but I suspect replacement parts are getting rare for these old beauties, the audio in socket died too but that’s a relatively easy drop out and replace item. I hope you find a solution for yours.
I just saw there’s some community work on creating a new replacement New OP-1 keyboard I recommend you follow this project