Yesterday my iPhone 12 Pro Max stopped recognizing my face, and I had to use my passcode to access my phone. While not a huge nuisance to enter the passcode, it did remind me how convenient it is for my phone to simply recognize my face. I thought that since I have been getting older, maybe my facial features have changed enough that I needed to re-configure Face ID. Therefore, I went to Settings > Face ID & Passcode > Reset Face ID. Although I was able to clear my current Face ID settings, I had a lot of difficulty configuring a new appearance.
As you can see from the 3 photos above, the Face ID setup asked me to position my face within the frame, and despite my compliance with the request, it kept asking me to move my iPhone a little lower. I dutifully pointed the iPhone lower and lower until my face was completely out of the frame.
On a couple of occasions, Face ID accepted my face despite my face being out of frame, but Face ID logins obviously did not work. Also, when trying to turn on the “Face ID with a Mask” feature, it would attempt to verify my face and fail to do so, stating “Your face must match the existing Face ID appearance.”
Naturally my first attempt to resolve the issue was to reboot my phone. Normally I do this by simultaneously pressing the volume up and side (power) buttons, and then using the “slide to power off” slider. Then I wait a little while, press and hold the power button to restart my phone. Unfortunately the Face ID setup was still misbehaving. My next attempt to resolve the issue was to ask the internet if they have had similar problems. I found an Apple Support page called If Face ID isn't working on your iPhone or iPad Pro and did everything it suggested, but none of the recommendations solved my problem.
In some discussion forums, users reported success with erasing all content on their devices to fix the Face ID issue, but I didn’t want to resort to that until I had exhausted all other options. Finally I found a discussion thread in Apple Support Community called Face ID stopped working on my iPhone after iOS 17 update in which Allensmith98 suggested restarting my iPhone in a different way: Settings > General > Shut Down. After powering up my iPhone, I was finally able to successfully configure Face ID.
I don’t know for sure if that is the definitive way to “reset” Face ID, as some users reported success with rebooting their phones using the volume and side buttons. In any case, it appears that the TrueDepth camera that powers Apple’s Face ID technology just needed a kick in the pants.