What Face ID is for

No details?

How to use Face ID:

Face ID not working?

Try the following:

▷ Update your iPhone. 📲

If that didn’t help, then try a Hard Reset:

1. Press volume up (quickly)
2. Press volume down (quickly)
3. Press and hold the power button until the Apple logo ( ) appears

If that didn’t work, it could be a hardware issue. ⚠️

Get expert service and support at the Genius Bar.

• Call Apple Support at 1-800-APLCARE.
• Contact Apple Support.
• Chat using Messages. 

Please explain further. If needed, follow the instructions in the link at the top of the page.