The access to Kubernetes integrated Docker platform is not available to everyone who registered for beta programme. Docker Inc has randomly chosen list of community members based on Dockerhub ID and only those users has got access to the build. Please note that even if you have registered as beta build doesn’t mean that you will get access to it while you update your latest Docker For Mac 17.12 Edge release. The selection is completely RANDOM and targeted at random Docker ID. Being part of Docker Captain programme, I received early access to the beta build through email. You might need to wait for their email. Hope it helps.