Q: AppleWatch not able to open Mac

Thank you. I did already the whole stuff, as I mentioned before. Up to here it works, but finally it doesn't as described. I use an iMac, 27" Retina, late 2014, Sierra 10.12, AppleWatch Series 2, Watch OS 3.

Thank you. I followed the instructions you mentioned. Up to here it works. But, as I described in my post, the final opening of the system doesn't work. I can see on the waking-sreen: "Unlock iMac with AppleWatch...". But it does not unlock within seconds. I'm asked to enter the passcode instead. And here is my problem.