Hey guys. I am trying to install Windows 8.1 in bootcamp on my 2015 15" retina MacBook Pro. It partitions fine, and I choose the ISO, but when it reboots to start the Install, I get a flashing folder with a question mark. I've tried a few times with different ISO's, same result. Does anyone have any idea how I can fix this? I am on the 10.11.3 beta. Thanks!