Please follow below instruction to do troubleshooting.
Monitor is not on
Make sure the monitor is on.
If you do not see a power LED (blue, green, or orange light) on the front of the monitor, press the power button until it comes on.
If no light comes on after several attempts, make sure the connections are properly connected.
Computer is asleep
If your computer monitor was on and you stepped away from the computer, then upon returning, it was black, it is likely that the computer is asleep.
Try moving your mouse, clicking the mouse buttons, or pressing any key (e.g. spacebar) on the keyboard to wake it up.
Check the data cable
Make sure the video cable you are using is firmly connected to the computer.
It is recommended that the video cable is disconnected and reconnected to be sure there is positive contact on the connector.
Check the power cable
Make sure the monitor is getting power by verifying there is a light (blue, green, or orange) on the front of the monitor.
If you see no lights on the monitor, make sure it is connected to a working wall outlet.
If the power cord is removable from the back of the monitor, try replacing it with another power cable.
If you still cannot power on the monitor after trying another wall outlet and cable, the monitor may need to be replaced.
Check the LED status
If the monitor has a light on the front, but that status light is orange, make sure the monitor is not in a suspend mode by moving the mouse or pressing a key on the keyboard.
It may be necessary to turn the computer and monitor off and reconnect the data cable on the back of the computer and on the back of the monitor.
Turn the computer and monitor back on.
Monitor settings are not correct
If adjusting the brightness or contrast has no effect on the monitor, continue reading through the other possibilities.
Problem with the computer
If the computer was working when the screen went blank, the computer might have a problem.
Try powering down the computer by pressing and holding the power button until the computer turns off.
Once the computer is off, wait a few seconds and then try powering the computer on again.