Dell U2415 No signal while being connected by Display port

Follow these steps to disable DP1.2 on the U2414H with NO signal input Buttons = Preset, Brightness, Menu, Exit, Power When you press the Menu button, the buttons then are = Up arrow, Down arrow, Check OK, Back, Power * Turn off the monitor * Unplug all video input cabling from the U2414H * Turn on the monitor * Press the Menu button * Press the Check OK button (3rd from left) and HOLD for 15 seconds * Then disable DP 1.2 Quoted from http://en.community.dell.com/support-forums/peripherals/f/3529/t/19564640