First of all, thank you for posting your question here at Fixya.com.
My first advice is to ensure that your AC source(outlet) is live. Try to plug it in to a known working outlet to confirm that the power source is not the issue. If you are using a surge protector/AVR, try to directly plug the monitor's plug to the outlet.
If you confirmed that the AC source is not the problem, then this is an indication that the fault is inside the unit. You have to check first the power supply board's fuse. Check its continuity, if it has a continuity, then the fault is on the voltage regulator circuitry and/or other circuitry on this board, I would advice you to replaced the entire power supply board. Click it here
for the replacement.
If you found it open, you have to replaced it with same current(ampere) ratings and then try to power on the unit again. You are lucky if the replacement fuse resolve the issue. Sometimes fuse fail due to voltage surge/flactuation, aging however if the new fuse didn't resolve the issue, then you have to replaced the entire power supply board.
Also, check if your unit is under warranty period, avail it because the manufacturer will fix it for free. Opening the rear cover will void the warranty.
Hope I helped you.
Have a nice day!
Good luck and take care!