So, I installed macOS Sierra and went to set up the automatic login to my Mac using my Apple Watch. I had everything set up right. I had the correct hardware. I had the correct software versions. Why can’t I get this work? I couldn’t even see the check box to “Allow your Apple Watch to unlock your Mac” in the Security & Privacy tab in System Preference.
I went through the whole turn off “two-step verification” on my iCloud account (appleid.apple.com) and turned on “two-factor authentication.” A little confusing but I did it as requested. So why can’t I set up using my Apple Watch to log into my Mac? I did everything right.
Well after many google searches and getting really frustrated I found an article on Macworld that had a little coda at the end where the author (Glenn Fleishman) shared his friends work around to this issue. He had to change his messages to use his Apple ID (settings->messages->send &recieve and then turn on “use my Apple ID”) to get everything working correctly. That was it! That fixed it! Why? I have no idea, but it worked. Hope this helps you too.