This morning my PC presented me with the wonderful gift of spontaneous failure, the kind no amount of googling will fix. My graphics card (MSi Twin Frozr 7850) decided to ignore my main monitor. I've tried almost everything: swapped (many) cords around, tried different setups (the 7850 recognizes all other monitors), and sacrificed a sheep on it. Nothing.
Basically, why does my graphics card not want to detect a specific monitor that I know for sure works with other PC's (even the mobo graphics too)? It just won't detect. I've reset the CMOS, update my BIOS, installed every graphics driver known, even promised a virgin daughter. I'm about ready to melt it down.
If you have two monitors, one that you know works with the computer right now, then you should connect both of them to your graphics card and boot up. On the monitor that works go into CCC and detect monitors and tell me what comes up.
After wards or right now check Devise manager and click on the monitors portion. If it says there is 2 monitors then that means the cables and ports work on the devices in question and is most likely a driver issue or how the computer selects which monitor is the native one.
check to see if you have a bad cable. sometime a wire can break or there a bent pin. i would see if there a hard reset and or any firmware updates for the monitor. to me it sounds like something went bad on the monitor so that it not turning on when the pc posts.