Hello, the preview button in Ignition wasn't working for me, and I've found a thread talking about the same issue. Unfortunately it was archived so I couldn't post there.
I just wanted to say that if it isn't working for you as well, make sure that Flash is ENABLED by default in your browser.
Inspecting the page I saw that the preview button loads a youtube video in a SWF Object (Flash) that won't work if you don't enable Flash by default, since the browser doesn't ask you to enable it.
I hope I helped you!