Tutorial : How to fix Apple Watch not automatically unlocking Mac

If your Apple Watch suddenly fails to automatically unlock your Mac, try the following solutions:

• Reconnect WiFi
• In Security & Privacy preferences, uncheck "Use your Apple Watch to unlock apps and
• Mac," then restart your Mac and turn the setting back on.
• Make sure your Mac isn't using internet sharing or screen sharing.
• Make sure your device is set up as follows:
  1. Your Mac has Wi-Fi and Bluetooth turned on.
  2. Your Mac and Apple Watch are signed in to iCloud with the same Apple ID, and your Apple ID has two-factor authentication enabled.
  3. Apple Watch has a passcode enabled.