Clamshell mode for Macbook Pro 15 Retina wit Dell P2415Q monitor
I'm running Yosemite 10.10.4 on a Macbook Pro 15 Retina. It successfully runs in clamshell mode with a standard resolution monitor. The Dell P2415Q works fine as a dual monitor, but goes blank when I try to activate clamshell mode. I know that others have made this setup work. What is the secret?
MacBook Pro (Retina, 15-inch, Mid 2014), OS X Yosemite (10.10.4)