Series X no controller. Not wireless, Not wired.

One day I woke up and my controller would not connect. I spent hours trying to get it to connect. At one point, after I slapped it, the pairing button on the console did work, but then it stopped again.

Now the pairing button does nothing. Using the Xbox app to go into settings and try pairing it doesn't work either. When I use a USB-C cable that works fine with my PC and controller, nothing happens. I took the Xbox apart and reseated the accessory board. When I pressed the pairing button, it flashed for a second and then stopped.

Between when it first broke and now, the Xbox sat unplugged for a few weeks. I tried updating both the Xbox and the controller, but that didn't help. The controller, as well as two others I tried, work perfectly fine with my PC over the same cable.

I also tried unplugging everything external just to test it: no fan, no disc drive, no front-panel USB, and no accessory module. Still nothing. There is no change in behavior. It won't sync over a cable or wirelessly.

When I plug the controller in, it vibrates once. If I press the Xbox button, it turns on but just keeps flashing as if it's searching for something to connect to.

Does anybody have any idea what could be causing this? $800 for a new one is a rip-off, and I really don't want to buy a used one filled with weed smoke for $400 on eBay when I bought this one new for $500 a few years ago.