Your Mac was unable to communicate with your Apple Watch.

Well, I wasn't having any luck having tried every single step listed in this forum multiple times. So, I checked for some updates to my Mac OS. I am running Mojave and had turned off all updates because this computer is used for professional audio production. To my surprise there were a couple updates... security and supplemental. Once my iMac rebooted after install, the first thing I tried was to enable the unlock with Apple Watch. It immediately worked... so fast in fact that I didn't think anything had actually happened. I logged out and re-woke the display... my watch logged me in faster than I've ever experienced. I hope this info helps those who are getting nowhere with the suggested troubleshooting.

I am now running MacOS Mojave 10.14.6.

This didn't work for me, until I *also* signed out and back in to iCloud on ALL devices (including iPhone the watch is tethered to). Not sure if the above solution is what did it, or the iCloud restart, or both -- but *solely* the Keychain & Library deletions didn't do the trick.

I had the same problem today and I tried all the solutions posted before, but no one worked.

What I did to solve the issue is signing out from iCloud on my Macbook after following the steps proposed by mark__t and the rebooting it while signed off.

After the reboot I signed in again with my Apple ID and the Auto Unlock functionality started to work again.

Maybe someone else could find my steps useful.

Try to Reset default keychains, this fixed my issue. check my solution above.

After 2-3 hour debugging, I fixed by "Reset default Keychains" from Keychain Access app > Preference, logout your user and make sure to enable Keychain again from Mac iCloud

Hi folks. Love the community discussions here and the tips that everyone provided. I've beat my head on my desk for weeks trying these steps over and over again. From deleting items from keychain, deleting files, unpairing the apple watch and setting it up as new and factory resetting my MacBook. None of those items worked for me.

I then went to my Apple Watch and turned off Wi-Fi. Trusting that the bluetooth phone to watch communication was working... I then went back into my System Preferences and re-enabled the Unlock with Apple Watch... BOOM it worked. I hope others find success with this! Let me know.

I had exactly the same combination of "changes".

To delete the plist files I simply started a terminal and went:

cd ~/Library/Sharing/AutoUnlock
rm *.plist

I followed these steps but it didn't work. What actually worked for me was going to the Apple Watch app on my iPhone, selecting passcode, and disable the 'unlock with iPhone' option. As soon as I did that my Mac recognized my Apple Watch when I enabled Auto Unlock.

I had to try the "KeyChain" solution several times. After deleting the files and rebooting my computer, it didn't work. I deleted files, stayed in, and tried pairing two times. The second attempt was successful, so keep trying!

Hello fellow sufferers. I realise this Discussion has got to page 21. I too have tried everything I can think of (thank you to Mark for your 12-step procedure. Thank you to all you agents in Apple Support for your valiant efforts). But nothing has worked for me.

Two days ago I thought of something I had not tried since getting WatchOS 7.1: restart the watch. And that has worked for me. Both our watches now unlock both our Macs. And it has stuck so far for 48 hours…

Sadly, no matter how many times I tried the above 12 step solution - it didn't work.

What finally worked for me - was:

1) Sign out of iCloud on my Mac

2) Reboot

3) Sign in to iCloud on my Mac

4) Reboot (not sure if this step was necessary, I did it to be safe)

5) Enable open with Apple Watch in settings

Et Voila - Success

What worked for me was enabling the Airplane Mode and then disabling it again.

Before this, I tried the steps outlined here https://discussions.apple.com/thread/251826134?answerId=253529745022#253529745022 and restarted my Mac without success.

But once I did the Airplane Mode trick, it worked.

iWatch unlock was always flakey but I only recently started getting the unable to connect message after the most recent round of updates. I also tried every suggestion on this thread to no avail until Signing out of iCloud on iPhone and signing back in again. So far so good ..... Thank You!

After a couple of days of it remaining flakey I decided to go nuclear and restore my iPhone 10 from scratch to the just realized 14.6 . It worked.

Even better.... It also resolved the bad battery drain (drained in 24hours with zero use) issue I had since 14 came along. This had also defied the myriad suggestions to fix (including a full restore) and seemed to be caused by background activities (mainly apple) that refused to turn off. Inspired by this I did a full restore to my IPadPro 11 which then cleaned up its battery drain as well. What makes this even more curious is yesterday there were reports of battery drain being caused by 14.6.

Steps

1. Backup iPhone to iCloud
2. Connect iPhone to Mac via finder
3. Initiate restore (ie update to 14.6) from the Mac (not via Wifi)
4. Restore backup via iCloud (wifi)
5. Update iWatch to 7.5
6. Re-pair iWatch and iPhone
7. On Mac preferences - security - "Use Apple watch..." turn it off then on again
8. Check handoff is on and same wifi on iPhone, iWatch and Mac.

FYI https://discussions.apple.com/thread/251826134?answerId=253529745022#253529745022 worked for me.

Finally worked!!!

I tried all the below steps and initially it didn't worked at all but then one step i feel is missing in this - RESTART THE MAC after the steps and then try. It worked :)