How can I fix my face recognition? It’s disable and cant be undone…

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. 

Hey there,

See Related Article again ☞If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support