My Face ID won't work on my iPhone
Why my Face ID don’t work for my phone
[Re-Titled by Moderator]
Why my Face ID don’t work for my phone
[Re-Titled by Moderator]
Unfortunately, we have no way of knowing.
However, by following all the steps in this article, you can find out and perhaps have it corrected as well.
If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support
My Face ID
My Face ID won't work on my iPhone