One thing I have noticed on the mobile apps (maybe the browser / desktop too) for Google Plus is that the video will be visible in my global feed, but the hangout is only visible if I look at the feed for the Treeleaf user.
So before the Zazenkai, I wait for the shared video to show up, then tap on the Treeleaf user icon, and then I'll see the hangout.
Gassho,
Sekishi