double click on mac mini to start touch id doesn't work
To add fingerprint I have to double click the power button on my mac mini but nothing happens.
Mac mini, macOS 14.6
A Mac mini does not natively have Touch ID and clicking its power button won't achieve anything. Do you have one of Apple's Magic Keyboards that has Touch ID built into the power button? If not, then you don't have Touch ID.
If you do have a Magic Keyboard with Touch ID, then see:
Manage Touch ID fingerprints - Apple Support
None of the instructions involve double-clicking a power button.
Regards.