Apple Watch 3 not unlocking Mac

I got an Apple Watch3 with WatchOS 4 and have my Mac updated to MacOS Sierra v10.12.6.

I followed all the steps to activate apple watch to unlock my mac. But it's not working. When I go to the last step to activate it, I have the following message: Unlocking your Mac not supported with your Apple Watch. (Update your Mac’s software to allow your Apple Watch to unlock your Mac.)... However I already have the latest MacOS version...

Any suggestion?