can't use face id anymore

Hello duyet,

Apple has several documents helping you with Face ID. Which document you refer to depends upon the issues you may be encountering.

This document explains what to do if you see a 'disabled' Face ID alert --> 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 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.

If Face ID is disabled this is most likely a hardware issue. Please update your iPhone to the latest iOS version, and if this is not working, please Contact - Official Apple Support to set up service for your device