The only biometric unlock option that the Pixel 4 offers is face unlock.
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.
For those affected, two subtly different error messages are appearing when they attempt to use face unlock, which could indicate two different but potentially similar problems: "Can't verify face". Multiple reports of annoying users of Pixel 4 have appeared online in the official Pixel support forum, as well as in Reddit, detailing the problem of facial unlocking, but so far, a concrete solution has not yet been discovered.
The problem first popped up starting around November, escalating in frequency over more recent months.
The issue manifested in various forms for Pixel 4users, who have reported about it on multiple platforms. Try again "message. The facial unlocking error has been reported both when trying to unlock the phone and in applications".
In some cases, the face unlock system simply stopped working after installing the January security update. However, Face Unlock didn't work even after the user re-enrolled face data. He wasn't also able to delete his face unlock data in Settings as he kept getting the message that read, "Cannot verify face". The issue doesn't seem to have resolved also after resetting the smartphone in safe mode. Some users have even tried to factory reset their device but it has not always been successful.
However, some of them say doing factory reset the problem was solved. The problem is, the owner of the device can't take a backup of the system like a fingerprint sensor.