I've seen many threads online of people not able to get oculus link to detect the quest 2 through usb cable. Since airlink is now available, most people will turn on airlink while they wait for a link cable to get to their house, assuming they didn't order it at the same time.
Having airlink on makes it impossible for wired link to work, and the only warning you get about this is when you turn on airlink, 2-3 weeks before your link cable arrives, so its easy to forget. There is no warning about this when trying to connect with a wire to your PC either. All the threads are suggesting bad specs, bad link cable, reinstalling drivers, etc. , but I've only seen 1 youtube comment suggesting to turn off airlink, which should be the first thing you check when troubleshooting, as it is the most simple fix. I hope this gets added to the troubleshooting webpage!
Cheers