After Android Police reached out to Google about the reports, the company said it was looking into them, but for any users still experiencing the issue after re-enrolling their face data, your best bet would be to contact Google directly. Google Pixel 4 saw a long-standing feature, the fingerprint scanner which will be replaced with the face unlocking feature.
Many of them first experienced the problem after installing the December security update, although it's not clear what causes the issue. Not only do you get to take advantage of the price cut, you'll also receive a $200 gift card when you buy either of these phones.
The issue manifested in various forms for Pixel 4users, who have reported about it on multiple platforms. In this case, the user kept getting a message after the update that face unlock might stop working and re-enrollment was needed. For some users, they began abruptly receiving notifications from the system asking them to re-register their face, despite the fact that facial unlocking works well. The message, "Can't verify face". But, if the user removes or re-add their face data to fix the problem then also the issue is not being solved. Deleting and setting up face data again hasn't worked, nor have simpler solutions like rebooting the phone. Even if you restart the phone in safe mode then also it is not helping out. If you are experiencing this issue, I hate to say it, but a factory reset might fix you right up. Some users have even tried to factory reset their device but it has not always been successful.