Your Mac was unable to communicate with your Apple Watch.

I had the same issue after installing iOS 14. I called tech support and was helped by senior technician who asked me to check a few things, deleted a couple of files in the startup folder and that did the trick. Has been working since. You may want call them and see if they can help you.

Good Luck

ccfromatl wrote:

I'm trying the solution from mark_t, but can someone direct me to where the "Keychain Access" is? I don't see anything in System Preferences besides a checkbox for Keychain that fits.

Applications -> Utilities -> Keychain Access

You can also use Spotlight (command-space) and start typing "keychain" and it should find it before you finishing entering the word keychain.

I had the same issue and tried all of the troubleshooting steps with no luck. I called Apple support and they wanted me to logout of iCloud and change my password. I logged out and then simply logged back in and then got it to work without having to change my password.

I had this problem after updating to Big Sur (iPhone X and Watch Series 3). I tried all of the suggestions here and elsewhere online to no avail. What did work for me was to reset my default keychain:

1) Open Keychain Access on Mac

2) Open preferences within Keychain Access

3) Click on "reset default keychains" and let it do its thing.

4) Restart Mac

5) Reactivate the "Use your Apple Watch to unlock apps and your Mac" within System Preferences. (It might take a couple tries to engage.)

Again, this did the trick for me after nothing else worked. This does erase all of your saved passwords within your keychain, but it doesn't take long to get things back up and running if you have your passwords for iCloud, Mail, etc. handy.

Thank you very much mtgags. I tried resetting but this did not work for me but it led me to a solution that worked. I restored an earlier ~/Library/Keychains from a Time Machine backup and it worked perfectly. Thank you again.

I found a suggestion on the web (appletoolbox.com) that this was a Handoff problem, and following their instructions was able to solve the problem.

Here's what I did:

1) On your iPhone (mine is on iOS 13.7), go to Settings | General | AirPlay & Handoff. If the "Handoff" setting is on, turn it off, wait for a few moments, then turn it back on.

2) Go to the Apple Watch app. On the main screen go to General, then look for the "Enable Handoff" setting. If it is on, turn it off for a few moments, then re-enable it.

3) Finally, on your Mac go to System Preferences | General and look for the "Allow Handoff between this Mac and your iCloud devices" setting. Again, if it is on, turn if off for a few moments, then re-enable it.

After doing this I went back to the Security & Privacy tab in System Preferences and tried to enable the "Use your Apple Watch to unlock apps and your Mac" setting. It immediately worked.

I might be stating the obvious, but if you found any of the settings in 3 steps above were "off", that may have been your problem as well...

This was the solution for me. I use lastpass as password manager, so "KeyChain" was switched off.

When I switched it on, it works like a charm. I did not see this in any instructions about enabling this feature.

I had the same issue with my Series 6 watch and experienced it when I download the first version of Big Sur. The only was I was able to solve it was erasing all contents and settings on my watch and re-setting up from a back up. This somehow got it realize that I actually have a watch paired to my Apple ID and it got my Mac to recognize my watch to unlock it.

after following mark__t's steps from stoska992 rebooting and redoing the steps several times i was still getting the error.

i eventually unpaired then paired the watch and on the first attempt pairing worked.

Possibly something on the watch needed a clearing out.

Thanks mark__t thanks stoska992

I tried all the solutions listed here and finally the thing that worked for me was signing out of iCloud on my mac and signing back in. Sort of a pain to get everything synced up again, but it did work!

Interesting - and this worked. The MacBook Pro simply had to have the setting checked again, and it worked without issue as it had before. My iMac Pro seemed to take a long time to connect after the box was checked and my password entered, but now it is working.

I don't know if simply uncaring and re-pairing with the watch would have done the trick, but all of the above with the un-pair and re-pair worked!!

Mark's added note to Steps 9 and 10 is important: Search for "ltk.plist and pairing-records.plist file in the Library folder" and delete them. Don't simply delete the files in the AutoUnlock folder. Following all of the steps above with the added step, then rebooting, worked for me.

Thanks.

I unpaired the watch for a previous problem. Am hoping to avoid doing that, since it wiped the settings from the watch. Not as painful as resetting the iPhone to factory settings, but still a pain.

I spent too much time with Apple Tech support yesterday. They had me turn off Screen Sharing. When I restarted the iMac, I lost their connection, of course. But I saw something that I had not seen for quite some time: 'When restarting, cannot unlock using AppleWatch'. That gave me hope. But when I put the computer asleep, the watch did not unlock when restarting.

Then they had me zap the PRAM. That did not help either.

I am going to try calling Apple Tech Support back today.

I had the issue, got passed up to at least level three of Apple support. She had me log out of my Apple ID, iCloud account, then log back in again. Magically, I could go to Security & Privacy to check "Use your Apple Watch to unlock apps and your Mac." It was scary logging out of my iCloud account, but I cannot see any downsides. Everything works after I log back in. It just feels dangerous when you have over 36,000 photos you don't want to lose. And there would be no way to import them into this computer.

It all works fine now for me.

This worked for me! I tried the "12 step" solution a couple of times, and it didn't solve the issue (Big Sur 11.0.x, Watch OS 7.1). I then upgraded to Big Sur 11.1, then on my Mac signed out of iCloud, rebooted, and signed back in to iCloud...and then enabled Apple Watch in security settings on the Mac. All worked. Thanks!