Q: The message "Your Mac was unable to communicate with your Apple Watch" Keeps appearing when I try to set up my Watch to unlock my MacBook Pro

Worked for me. Thanks!

Beautiful. Thanks!

Watch app in the iPhone---> general ---> switch "enable handoff" off ---> turn it back on

That's what just worked for me, give it a try

This worked once I paired my iphone with my mac via bluetooth.

SOLUTION!!! I kept getting the message saying the MAC couldn't connect to Apple Watch. Tried every single solution I could find..EVERYTHING! Spent an hour with escalated support and we found the solution on accident. It was the iCloud Keychain causing the issue. Here's the solution:

1. Open Finder, click GO and hold OPTION.
2. Click "LIBRARY" and Open the "KEYCHAINS" folder
3. Find the folder with a bunch of numbers and letters as the folder name and drag it to your desktop
4. Next go to System Preferences...and into your iCloud settings. You will see that your keychain is now off.  Enable the keychain by checking the box.
5. Once the keychain is enabled...go through the regular methods to set it up: Automatically unlock your Mac with your Apple Watch - Apple Support

Didn't work for me

My MacBook was happy to communicate immediately but my iMac refused to communicate ..... until eventually after several further attempts it did communicate with my Apple Watch. I did not change any settings on the Watch, iPhone or iMac; it just worked .... eventually.

my issue is slightly the same. i had this working fine until apple had to replace my watch. since i've gotten the replacement watch it gives the error message. i have tried everything suggested on this thread and no dice. any other solutions?

This worked for me - or at least triggered me getting it to work.

All was good for me initially when I installed WatchOS 3 on launch day, but when I replaced my 6s Plus with a 7 Plus I think it broke, and it took moving out the Keychains folder to fix it, as well as turning on Keychain on my iPhone (which had turned off for some reason, as had my iPad Pro).

I had de same issue, but as soon I disabled and re-enabled Hand-off settings on my MacBook, it started working again.

I tried everything listed here with zero effect, sinking far too many hours into it.

I tried again this morning, and it failed. Then I updated to iOS 10.0.3 and it worked immediately.

YAAAAAAY