Can the Face ID error be fixed??
Can your iPhone Face ID error be corrected?
Question marked as
Visit an Authorized Apple Service Provider or Apple Store and let them diagnose the iPhone.
They can fix this issue.
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3 . If you still can't enroll your face or unlock your device with Face ID, you can take your device to an Apple Store or Apple Authorized Service Provider, or contact Apple Support about your iPhone or your iPad.
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copied from: If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support