My iPhone Face ID just suddenly stopped working with no reason detected as the cause

Hi Chjnbhi,

If Face ID is not working, you'll need to follow the steps outlined in If Face ID isn't working on your iPhone or iPad Pro - Apple Support

"If you still can't enroll your face, contact Apple Support.

Only a trained technician should service your device. Improper repair, modification, or use of nongenuine Apple components in the laser systems might prevent the safety mechanisms from functioning properly, and could cause hazardous exposure and injury to eyes or skin."

Cheers.

Me too. Managed to reset it yesterday, only to find its gone again today. When I tried to reset it again, I got the message, "Face i/d not available, try later"

What's going on?

Same. This phone has given me issues from week 1 of coming out of the box.