Just upgraded to V9...now I see no ENTER PREVIEW in menu????
That was removed some time back because there were technical problems including system resources and OS changes. It would be a challenge to give users a good experience. We've added the ability to hide the Timeline and then going full screen.
There is a feature request vote for returning the Preview function. It was removed in version 7. Do vote for it as user interest can impact development priority.
Link to Old Telestream Community Forum