Okay, since no one else has responded, I'll throw in my $0.02.
I had purchased a mechanical keyboard from a thrift shop, it didn't work. Opened it up (rebranded KeyCool, didn't even have to use tools to open it), didn't see anything obviously wrong. Neither Windows nor Linux would detect it as a USB device. I didn't bother returning it, but months later I bought another mechanical keyboard with missing keys and on disassembling it I noticed that it had the same form of connector for the keyboard cable as the KeyCool did.
I took the cable out and disassembled the KeyCool again, swapped in the cable, and plugged it in to a computer. I received a USB error on the PC, but that was more than I'd gotten before with the KeyCool. On closer inspection I found that the connector itself may be the same but the pinout was different.
KeyCool:
AUKEY:
So I disassembled the connector and repinned it to match the KeyCool, socketed it, and plugged in to the computer again. The dead keyboard came back to life, all the keys worked, the various lighting modes worked, it was fine. I connected the original cable to the keyboard (it was just a USB-C adapter) and plugged it in with a modular cable and the keyboard still worked. Reassembled and tested yet again, still golden.
I repinned the cable from the other keyboard back to its original state and put it back with the keyboard it came from.
What I think happened is that something was screwy in an IC or a discrete component, and sending in 5V through the wrong pin with the data pins in the wrong order somehow reset something the hard way. It was enough that the computer could recognize something but clearly wrong. But it was enough to make it work again after plugging it in the right way.
So, caveats, I am not a chip-level electronics expert. I have lightly dabbled in board-level where discrete components have failed (especially capacitors) but I am a rank amateur, a bull in a china shop with this sort of troubleshooting. I would not actually recommend anyone do this unless they were basically ready to throw away the device already, and frankly I'd not even use a PC I cared about in case the mis-pinning fried the USB chip inside it. If you have something like an old USB hub that you could plug into your PC, or you have an old PC that you don't care about, you could look at rearranging the power and data pins if you can access the connector, but it's not something that anyone could especially recommend.
Good luck in your attempts to repair, it's frustrating when something that you're attached to breaks.
