How to fix Apple iPhone X Face ID feature that is not working

Your current Face ID information may have been erased as a result of the upgrade, and it is no longer functional. If this is the case, you'll need to reset Face ID before resetting it. Here's how you do it:

1. From the Home screen, choose Settings.
2. Choose between Face ID and Passcode.
3. Then select Reset Face ID from the menu.
4. To reactivate Face ID, tap Set Up Face ID and follow the onscreen instructions.