Step 1: Remove Auto Unlock Entries from Keychain

  1. Open Keychain Access from Applications > Utilities.
  2. In the menu bar, select View > Show Invisible Items.
  3. Use the search bar to find entries named “Auto Unlock” (with a space) and “AutoUnlock” (without a space).
  4. Delete all matching entries.

Note: It’s normal if some entries reappear later; the system will regenerate them.

Step 2: Delete Auto Unlock Files from Finder

  1. In Finder, press Command + Shift + G to open the “Go to Folder” dialog.
  2. Enter ~/Library/Sharing/AutoUnlock and press Enter.
  3. Delete the files named ltk.plist and pairing-records.plist.

Step 3: Restart Your Mac

After deleting the relevant Keychain entries and files, restart your Mac to ensure all changes take effect.

Step 4: Re-enable Auto Unlock

  1. Open System Preferences.
  2. Navigate to Security & Privacy > General.
  3. Check the box for “Use your Apple Watch to unlock apps and your Mac”.

You may need to enable this setting twice; the first attempt might fail.

Source: https://old.reddit.com/r/watchOSBeta/comments/j6b604/for_those_that_have_had_difficulties_enabling_the/