Why my Face ID not Available

See these support articles:--> Use Face ID on your iPhone or iPad Pro – Apple Support

and/or this one:--> If Face ID isn't working on your iPhone or iPad Pro – Apple Support

If the issue still persists, contact Apple Support directly, using this link:-->Get Support

Regards

Giulio

If you still need help, reset Face ID, then set it up again. Go to Settings > Face ID & Passcode and tap Reset Face ID. Then tap Set up Face ID to set it up again. If you can't enroll your face, take your device to an Apple Retail Store or Apple Authorized Service Provider or contact Apple Support.

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