Kindly follow the below mentioned steps which could help in isolating the issue:
•Go to BIOS and confirm if there is video.
•Reseat monitor cable (VGA/DVI/HDMI) and check the input signal mode in Monitor OSD.
•Swap monitor power cable with the tower. If works, Replace “Power Cable” only. Else, drain flea power, Remove any 3rd party peripherals and power cord from your Desktop, press and hold the power button for 20 seconds to discharge any residual current inside the desktop.
•Press Monitor power button to check LED Status. If the Monitor power button LED does not come on, “Replace Monitor only”.
Thanks & Regards