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. Some are also unable to even delete the phone's stored face data in Settings.
The problem has manifested itself in several ways for Pixel 4 users, who have reported on it on multiple platforms. For affected users, it is a very annoying problem since they can not unlock their smartphones easily.
As per the reports, the users of the Pixel 4 device has got a message which says, "can't verify Face", and "Hardware not available". These users are receiving error messages while trying to unlock the phone with their faces. In some cases, the facial unlocking system simply stopped working after installing the January security update.
The failure of the feature has been reported both during an attempt to unlock the phone or while launching a biometric-protected app. Once the Pixel 4 was launched, users discovered that face unlock had one critical flaw when compared to Apple's, as it didn't have a Require Attention option - that someone could unlock your phone by holding it against your face while you sleep.
However, the problem not universal and only a small number of people apparently facing the face recognition issue on their Pixel 4. However, it is also occurring without getting the update. Although there are quite a few users affected, it does not seem to be a problem that affects most users.
A reboot restores the face unlock function to normal again, but this solution doesn't work for all users either. However, doing so failed to fix the issue.