Check with Device Manager, if you've IR based webcam for facial recognition is properly installed.
Please note, Windows Hello Face recognition, doesn't works on normal or regular webcams.
If your device doesn't have IR based webcam, you can attach and IR based external camera.
Also, you refer suggestions in this article:
https://www.kapilarya.com/fix-facial-recognition-not-working-in-windows-11-10
Let us know if this helps!
Note: Included link(s) in this reply refers to a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.