https://www.theverge.com/circuitbreaker/2017/9/12/16296912/apple-iphone-x-face-id-demo-fail

Moments after Phil Schiller got done extolling the accuracy of the iPhone X’s brand new, ultra-sophisticated Face ID authentication system, Apple’s software chief Craig Federighi came on stage to show how easy and fast it is to actually use. Unfortunately, Federighi’s initial attempt to unlock the on-stage demo iPhone X was unsuccessful. The passcode screen popped up.

For all we know, this was a one-off fluke that’s not indicative of how well Face ID will actually perform for consumers. In fact, it doesn’t seem to be an error by the company’s replacement for Touch ID at all. The passcode screen that Federighi got said “Your passcode is required to enable Face ID.” This is the same screen that would come up on existing iPhones after a device has been restarted — or simply after several hours have passed without authenticating through the lock screen. This is a security precaution introduced with Touch ID that will clearly carry onward with Face ID.