Apple's XS face ID lock can't be used, which is caused by an unexpected failure of Apple's mobile phone system program. This problem can be solved by resetting the face ID. The specific process is as follows:

1. Take iphoneXS as an example, unlock the mobile phone desktop, find the "Settings" icon selected in the red box, and click Open to enter.

2. In the setting interface, find the "Face ID and Password" icon selected in the red box, and click Open to enter.

3. Enter the set mobile phone password and open it to enter the next step.

4. Find the "Set Face ID" option icon and click Open to enter.

5. According to the system requirements, click "Start Using" below to record face recognition.

6. Wait for the face recognition setting to be completed, and click "Finish" below to complete the face ID setting.