I have copied the text from a previous forum post, since I am having precisely the same issue (it was resolved via PM):

When I've purchased my Razer Book the Windows Hello facial recognition worked well and was almost instant.
Two months later I've noticed that Windows Hello is barely recognizing me. Usually, it just says that it couldn't recognize me but if I try hard then it's eventually recognizing me, but just sometimes. I've tried disabling facial recognition, enabling it again, scanning my face multiple times but no luck. Funny part is that once it was recognizing me while wearing glasses but not without them.

Disabling "Windows Hello Face Software Device" and restarting PC didn't help.
One possible non-software reason for this is that I could've somehow damaged the infrared camera while cleaning my screen with wet wipes, but I was careful when I did so, so I'm skeptical about this.

Is there any Razer driver for the integrated camera out there? Maybe there are some diagnostics or calibration tools? Any advice would be appreciated.