Why did my Face ID not work

Hello,

Apple has several documents helping you with Face ID.

This document is specific to seeing a 'disabled' Face ID alert, and explains what to do when you see that notice. --> If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support

If you don't see a 'disabled' message but do have general issues with Face ID not working properly, explore the list of things to try in this document: If Face ID isn't working on your iPhone or iPad Pro - Apple Support

If the first 8 don't solve the issue then use #9, contact Apple.

Hello ~ If working back through the steps in the article you came from doesn’t help you may need to have your iPhone checked…

Genius Bar Reservation and Apple Support Options

Also you may go to lower left and click on Support.

~Katana-San~