My HP ZR24W monitor shuts down after only a few seconds. It doesn't matter if it is DVI/VGA/DP plugged or standalone. It doesn't power off, just turns off the display as if it is in power save mode; however, the light stays blue. If left on, it does turn amber eventually. The only thing that is ever displayed is the "Check Video Cable" option if it is not plugged into a video source. but it flashes on for about a second then the screen goes black. Any ideas?