Check whether the device is soaked or bumped: If your phone has been accidentally soaked or dropped recently, check whether the face ID is unusable. Don't take relevant measures on your own. It is recommended to send it to the official after-sales service as soon as possible.
Check whether the screen has been replaced: If your device is replaced with a third-party screen, face ID will not work properly. Therefore, it is not recommended that you buy a second mobile phone whose face ID cannot be used. Most of them have screen problems.
Restart the device or update to the latest system: If there is no accidental damage to the mobile phone or hardware problems, and the prompt "Face ID unavailable" appears, it is recommended to try to restart the device first. If it still doesn't work, please update the equipment system to the latest version.
IPhone often can't recognize facial information: If your face ID can be used to input facial information, but it often fails to unlock it, it is recommended to check whether there is a problem with the phone film first, or try to re-enter facial information. You can also set an alternate appearance: Go to Settings -Face ID and Password, and then click Set Alternate Appearance to start setting.