1. Check Power
Check to make sure the monitor is turned on, which is usually indicated by some kind of light on the power button itself.
If the light is on, the monitor is on and you should see some message.
If the monitor is on, but nothing is showing up, try to press the menu button to bring up the built-in monitor controls.
If still you have a blank screen, then this could mean there is a problem with your monitor.
Even with nothing connected, you should be able to bring up the monitor menu.
Try connecting a different monitor if you have one.
If a separate monitor works fine, then it could mean the power supply is bad on the original monitor.
Try replacing the power supply, if an external power supply is available, and see if that fixes the issue.
Now check to make sure the computer is properly turned on.
The main thing here is to check for any warning lights or unusual beeps when you power on your computer. If the power button or one of the status lights is red or orange or if the computer beeps several times when turning on, this is indicative of an internal problem.
If the power is on and everything looks fine, but you’re still not getting anything on your display, the computer may have gone into standby or sleep mode and isn’t being woken up. Try pressing keys on the keyboard or moving the mouse. If none of that works, try restarting the computer by pressing the power button.
2. Check Cables
The next easiest thing to do is to check all the cables. Whether you are using VGA, DVI, HDMI or DisplayPort to connect your computer to your monitor, cables can sometimes become detached. This is especially true for cables that don’t screw into the back of a monitor.
Make sure you check the connection at the PC and on the monitor. For those of you who have more than one video card, you need to be careful how you connect the monitors.
If you have a dedicated graphics card, then make sure the monitor is connected to the graphics card and not to the motherboard video connection. By default, Windows is supposed to disable the motherboard graphics automatically when you have a separate graphics card, but sometimes this doesn’t happen.
If the cables are connected and you only have one video connection, then you need to rule out bad cables. To do this, you need to find another monitor to connect your computer to. If the screen is blank on the second monitor also, then it could be an issue with the video cable.
Try replacing the video cable or using a different video cable if you have multiple connections options like DVI, HDMI, etc. If using VGA works, then it could mean there is an issue with your HDMI or DVI cable.
3. Check Source
Lastly, you should also make sure that the input source on your monitor is set to the correct input. Most monitors normally auto-detect the input source, but sometimes this feature can become disabled. Press the number 2 button on your monitor to scan input sources, it will automatically scan all sources and stop when a source is detected.