If your Apple Watch won't unlock your Mac, here are some fixes you can try!

When Auto Unlock works, it's magical. You open or approach your Mac while wearing your Apple Watch and, instead of having to type in your — hopefully long, strong — password, it just logs you in. No fuss. No muss. But when it's not working — anger, frustration, blame, recriminations, and having to type in that — hopefully long, strong — password. So what can you do when Auto Unlock doesn't work?

Check your sets

It's embarrassing, but it happens. Sometimes even though you're sure you set up auto unlock right, something may be wrong. And there's a lot of possibilities here:

  1. Passcode set up and entered on your Apple Watch.
  2. Login password set up on your Mac.
  3. Two-factor authentication set up on your Apple ID.
  4. Auto Unlock enabled in System Preferences on your Mac.

Read — and re-read — how to set up auto unlock on your Apple Watch and Mac

If you find a switch you forgot to flip, great! If not, let's keep going!

Reset the radios

Auto unlock requires Bluetooth 4.2 and Wi-Fi to be up and running on both your Apple Watch and Mac in order to work. If one or both radios have been turned off on one or both devices, or somehow stopped responding, Auto Unlock will likewise stop working. Cycling them can sometimes jump start everything back into action.

On your Apple Watch:

  1. Swipe up from the watch face to bring up control center.
  2. Tap the Airplane Mode button to turn all radios off. (It'll turn yellow when they're off.)
  3. Tap the Airplane Mode button to turn all the radios back on. (It'll go back to black and gray when they're on.)

On your Mac:

  1. Click on the Bluetooth icon in the menubar.
  2. Click on Turn Bluetooth Off.
  3. Click on the Bluetooth icon in the menubar again.
  4. Click on Turn Bluetooth On.
  5. Click on the Wi-Fi icon in the menubar.
  6. Click on Turn Wi-Fi Off.
  7. Click on the Wi-Fi icon in the menubar again.
  8. Click on Turn Wi-Fi On.

Once you're done, try auto unlock again. If it works, great. If not, keep reading.

Reboot everything

The next thing to try is a hard reset. Make all the "reboot Windows" jokes you want but it's a cliche for a reason!

On your Apple Watch:

  1. Press an hold the Digital Crown and Side button at the same time.
  2. Keep holding them down until you see the Apple logo.

On your Mac:

  1. Click on the button on the menubar.
  2. Click on Restart...

Once you've rebooted, auto unlock will be temporarily disabled. Enter your password to re-enable it. Then let you Mac sleep and try auto unlock again.

Check for updates!

Apple's Bluetooth and Wi-Fi stacks—the set of software that controls the radios—aren't without occasional quirks. Sometimes, new versions of watchOS or macOS introduce compatibility problems; other times, they fix them. If you're having Bluetooth or Wi-Fi connectivity problems, you're better off updating than not. If it's already broken, the update is your chance for a fix.

On your iPhone:

  1. Launch the Watch app on your iPhone.
  2. Tap on the My Watch tab at the bottom.
  3. Tap on General.
  4. Tap on Software Update.
  5. If there's an update available, tap to install it.

On your Mac:

  1. Launch the Mac App Store.
  2. Click on the Updates tab, top left.
  3. If there's a macOS software update available, click to install it.

Once you're done updating, try to use auto unlock again — after you've logged in following reboot to re-enable it! If it works, awesome. If not, there's even more to try!

Re-pair your Apple Watch

Re-pairing your Apple Watch is a huge pain, but if something has gone wrong with the connection between your iPhone and Apple Watch, secure information won't be transmitted properly, and that will stop auto-unlock dead.

  1. Launch the Watch app on your iPhone.
  2. Tap on the My Watch tab at the bottom.
  3. Tap on [Name]'s Apple Watch at the top.
  4. Tap on the Info button on the right. (Looks like an i.)
  5. Tap on Unpair Apple Watch.

Once your Apple Watch has been unpaired, repeat the pairing process, restoring from your most recent backup. You'll have to re-enable Auto Unlock in your Mac's System Preferences again, but once that's done, auto unlock should be back up and running. If not, you have one option left...

Contact Apple

Sometimes a problem really is a problem. Like any electronics, Bluetooth and Wi-Fi radios and the various connections to them can have problems. If you have AppleCare+, don't walk, run to your local Apple Store to get it looked at.