Face ID not working on my iPhone

When Face ID doesn't work, it usually indicates an issue with the TrueDepth Camera, either a software issue or something obstructing it, or a hardware issue. Please first troubleshoot with these two Support Articles.

If Face ID isn't working on your iPhone or iPad Pro - Apple Support

If an alert says Face ID has an issue on your iPhone or iPad Pro - Apple Support

If those don't help and the issue persists, this would be indicative of a hardware issue. As a result, I suggest you make a reservation at your nearest Apple Store Genius Bar or Apple Authorized Service Provider.

Genius Bar Reservation and Apple Support Options - Apple

Hello!

See this: If Face ID isn't working on your iPhone or iPad Pro - Apple Support

Have a great day!