MY IMAC HAS OSX YOSEMITE VERSION 10.10.5, PROCESSOR 3.2 GHZ INTEL CORE I5, 8GB 1600 MHZ, NVIDIA GeFORCE GT 755M 1024 MB. I INSTALLED UNREAL AND WHEN I HIT THE LAUNCH BUTTON IT JUST CLOSES THE EPIC GAMES WINDOW AND I JUST GET A REALLY QUICK “BUISY” NOTICE UNDER THE UNREAL BUTTON. WON`T IT WORK IN MY MAC?