Touch ID has disappeared from my system preferences, how do I get it back
How do I get Touch ID back on my iMac?
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Did you already try the troubleshooting tip for the Magic Keyboard?
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7 . For Magic Keyboard with Touch ID, turn your keyboard off and on, then connect your keyboard to your Mac with the USB to Lightning cable. After you turn Magic Keyboard off then on, Touch ID may be unavailable for up to 10 seconds.
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