Win 10 update broke my backlight/Fn Key (X240)

[DavidGould]

This happened at least 8 months ago. Using a keyboard tester, Windows no longer recognises the Fn key in the bottom left of the keyboard. Since then I've been forcing Fn lock, but now can't use F1-F12. Nor does the spacebar or Fn+Space do anything.

So I suspect the keyboard driver got changed/replaced. My installation is using MS' standard PS/2 keyboard driver now. I'm unable to find an old ThinkPad keyboard driver, nor map anything to the 'keycode' that the software expects. Of course, I didn't notice the problem before the rollback deadline. When it was last working, I remember it being a clunky solution even then.

Using up-to-date Win 10 on a ThinkPad X240.

[axur-delmeria]

Have you tried this: https://pcsupport.lenovo.com/us/en/prod ... s/ds120449

[DavidGould]

Have you tried this: https://pcsupport.lenovo.com/us/en/prod ... s/ds120449

Funnily enough, I came here to say that I had tried that -- once before I posted (but wasn't sure) and once after. I read something about how this sort of thing is a keyboard driver for the function keys.
An older version didn't help. I've yet to try uninstalling the Power Management too. Bing Chat was helpful on this, being presumably trained on MS help pages & documentation.

I apparently found a way to revert to 21H2 using DISM /Remove-Package. It didn't fix the problem and I don't think 22H2 broke it. I'll try removing a couple more packages.

I can also try to Reset my PC or I can try installing a 21H2 ISO. I suspect only the former will allow me to keep my software.

It's also possible the key is broken. It wasn't very clean under the key but the actual rubber/silicone seems to be waterproofing and sealed to the keyboard PCB. But Fn keys are non-standard and I don't know how to test it outside of Windows. The key lights up setting Fn Lock from Windows (Control Panel -> Keyboard). Also the Hotkeys service is running.