Unable to log in using Face ID

To use a passcode instead of Face ID, swipe up from the bottom of the device while holding it as if you were going to use Face ID.

To reset Face ID, go to your Settings app, then "Face ID & Passcode", then tap “Reset Face ID".

Read this support article about SDP limitations when trying to reset certain security related features: About Stolen Device Protection for iPhone - Apple Support

Use Passcode instead.

See the pic below which is self-explanatory

Probably you have "Always" Ticked in place of "Away from Familiar Location"

For enhanced security, there's a one-hour delay when changing your location settings from "Always" to "Away from Familiar Location." This applies even if you use Face ID for authentication.



A delay will be required when you are not at a familiar location, such as your home or work, to change security settings.

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