I have a Mac Pro 5,1 and for some reason I am unable to reboot into Windows 10 when I have it selected in the System Preferences pane as the startup disk. When I do that I get a flashing cursor or I get a message on the screen saying there is no bootable media or a message like that. And when I select "reboot into OS X" or select OS X as the startup disk in Windows it does nothing and boots to windows. The only way for me to switch is to use the option key. Anybody have any ideas on how I can fix this? I already updated the boot camp utility in windows to 6.1 but it didn't work. I initially had problems in the start where Windows detects GPT disk as MBR in EFI boot so I had to follow this guide to fix that but I'm not sure if that affected my install.