Face ID stopped working 17.3.1
Face ID had been working fine but now with 17.3.1 it will not unlock my phone. I have gone into settings and reset the Face ID, rescanned my face and it still doesn’t work.
iPhone 15 Pro Max
Check this link...
If Face ID isn't working on your iPhone or iPad Pro - Apple Support
If that doesn't help, you my need to make an appointment at the nearest Apple Store for a repair...
Apple Store - Find a Store - Apple