Can't Play New Launcher in Fullscreen

Ever since the Dev version, if I try to play the new launcher, the screen goes blank. The only way to escape is to hit the power button, and then it reverts to small screen. If you try to get it back to fullscreen, the same happens. I thought this just might be a quirk that they'd fix once the full version came out, but it hasn't changed. I have a MacBook Pro, if that helps.