A few days ago I upgraded from macOS Sonoma 14.6.1 to macOS Sequoia 15.1.1. This morning, I noticed TouchID wasn’t working on my external Magic keyboard attached to my Mac Studio to unlock my computer, even when I’d been using the computer just 5 minutes before (screensaver had enabled which I have setup to require authentication to get back to the computer from). I knew this was new behavior because I love unlocking my Mac using TouchID and do it all the time. I went to follow the suggested solution by leroydouglas in this post (Touch ID not working – Apple Community), and when attempting to perform Step 5 (“Choose Apple menu  > System Settings (or System Preferences), click Touch ID & Password, then turn on the setting to use Touch ID to unlock your Mac.”), I noticed that I could not change any of the toggle controls on that screen; they were all off and grayed out (disabled). So, I rebooted, and went back to that screen, and they were all enabled again, and modifiable.

So, if you run into this, a simple reboot may do the trick.

I couldn’t say if TouchID for general uses e.g. purchases wasn’t working because I rebooted before I thought to test that, but I suspect it would have failed also, so I suspect this would be as solution for that as well. It’s like the secure authentication between the Mac and keyboard wasn’t there until I rebooted.

[See post on Apple Communities]