I had to work on a system yesterday night for my neighbor that deactivated when they updated the BIOS.
Turns out Microsoft did an update last month to their activation servers which finally removed the "free update" upgrade for Win7/8/8.1 systems that expired back in 2016. You know, the one that allowed you to update for free using the Win7/8/8.1 keys.
However, it had the unexpected side effect of causing activation problems on some systems that were legitimately upgraded via the process before the cutoff date. I know my neighbor's system was updated before the cutoff, as I did it for him. For some reason, he got the urge to update his BIOS and it deactivated his Windows installation.
MS customer support totally blew him off when he called (by multiple support reps, including an escalated support call), so we ended up having to buy another key from a "reputable third party" to get his computer up and running again.
Apparently, it is a known thing -- if you upgraded using that "loophole", don't change any hardware or update your BIOS or you may need a new Win10/11 key. Microsoft has acknowledged the issue and is supposedly "investigating".... which I read to mean they have no intention of doing anything about it.