Mac Auto Unlock stopped working for me after upgrading to watchOS 7. Fortunately I did not have to search for a solution. A user fix explained on the Apple Support community board worked for me and was easy to do. The steps are:
- Open “Keychain Access”
- In “View”, enable “Show Invisible Items”
- Search for “Auto Unlock”
- You should see a whole bunch of application passwords for “Auto Unlock: XXXX’s …”
- Select all records and delete (this will reset/disable auto unlock on other Macs if you use multiple Macs)
- Whilst still in “Keychain Access”, search for “AutoUnlock” (no space)
- There should be 4 entries for “tlk” “tlk-nonsync” “classA” “classC”
- Select 4 records and delete (don’t worry if they re-appear, the system repairs this automatically)
- Open “Finder” and navigate to “~/Library/Sharing/AutoUnlock”
- There should be two files “ltk.plist” and “pairing-records.plist”
- Delete both files
- Open “System Preferences” and try enabling auto unlock. You may need to enable it twice, the first attempt will fail.
Instead of going straight to step 12, I restarted my MacBook Pro after deleting the files in step 11. Auto Unlock worked right away after enabling the option in System Preferences.
As always make sure you have a recent backup of your Mac before doing this. With macOS Big Sur on the horizon regular backups are the best preventative measure you can do, also follow Howard Oakley’s Big Sur preparation advice. It’s the Mac equivalent of COVID era hand washing and face masking.
The watchOS 7.1 update fixes this issue, also the fix outlined above has only been used on macOS Catalina, it may not work with macOS Big Sur. There are also reports that logout/login of your iCloud account on macOS, be sure to search for the latest information and advice.