Face ID not working

Per details from within reference article, accompanying your topic thread:

"A problem was detected with the TrueDepth Camera. Face ID has been disabled."

What to do next

1. Update your iPhone or iPad to the latest version of iOS or iPadOS.
2. If you still can't enroll your face or unlock your device with Face ID, you can take your device to an Apple Store or Apple Authorized Service Provider, or contact Apple Support about your iPhone or your iPad.

"Only a trained technician should service your device. Improper repair,

modification, or use of non-genuine 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..."

Links within blue-text above, explain the route to get service on your product.

This only if you cannot get the symptoms of failure to be resolved by following

the first part of the instructions; by updating the iOS system software.

Please give some details about your device (like which model is it, etc…)

If you are using iPhone 11 or earlier and iPhone X or later:

• Please note that these models scan your face and unlocks it ONLY IF you don’t wear a mask

If you are using iPhone X or later:

• If you turned on Attention for Face ID (which can be found on Settings -> Face ID & Passcode) then you must not wear sunglasses or any type of glasses that make your iPhone not be able to detect your eyes looking at the phone.
• If any of these solutions don’t work, then I’m afraid your iPhone’s screen isn’t authentic (AKA the screen’s missing the TrueDepth camera) so you should head to an Apple Store or an Apple authorized store to get replaced with an authentic screen.

I hope these will solve your problem.

Have a great day!