My mobile face id not working

Hi, make sure your ios is updated to the latest 14.7.1

Try a hard reset:

1. Press and quickly release the Volume Up button.
2. Press and quickly release the Volume Down button.
3. Then press and hold the Power button until the device restarts.

also read this: https://support.apple.com/en-us/HT208114

See if anything here helps 

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