Face ID got broken on iPhone X with the iOS 11.2 update? Here's how to fix it
Some users of Apple's priciest iPhone were complaining that Face ID stopped working on iOS 11.2. Their phones showed the weird "Unable to activate Face ID on this phone" message when faced into a staring contest. The reason for this particular drama is unknown, and it only happens to some iPhone X units, so if it had passed by your unit, sight with relief.
If not, and you are getting the above message when trying to use Face ID, simply reboot your X, which is most cases fixes this "bug." Press and hold the side power key, and any one of the volume buttons, then swipe the slider to the "off" position until your screen goes dark. Wait a bit, then power up the iPhone X with the side button, and you should have Face ID working properly again.
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