hi guys, i have recently purchased a Dell U2711 monitor to use as an external monitor for my Macbook Pro Retina 13(Late 2012). The reason i wanted this monitor because of its resolution(2560x1440). I bought a mini display port to display port adapter to connect to the monitor but all i get is black screen from the monitor. However on my MBPR, it seems that it recognised the monitor because under system preference->displays, the arrangement pops up and i am able to arrange my display position, and when i clicked mirror display it shows that my MBPR is connected to the monitor(as per screenshot below) and i was able to choose the 2560x1440 resolution. Even if i changed the resolution to 1080p/720p, the monitor continue to show black screen( it shows no connection to display port) I have tried using HDMI cables, it worked perfectly. I am on the latest firmware(10.12) sierra PS: Typo on the title, its late 2012 not 2011 May I know how can i resolve this problem ?