My monitor is blank and the light flashes green

Verify monitor operation by UNplugging it from the computer and turning it on. A "Self Test Screen" shall appear (if it doesn't, the monitor is faulty and must be repaired).

Assuming it worked, plug it again and turn it on. After half a minute or so, turn the computer on. You should be able to see at least the BIOS POST screen: if you don't, there could be something wrong in the computer video board (maybe misconfigured, or set to output to a different, possibly internal, head - I saw it once with a Matrox VGA). Refer to the VGA manual for that.

If the POST screen appears, the problem is perforce in the OS VGA configuration. Assuming it's Windows, you can get into the safe mode boot screen by pressing the F8 key at boot, and once booted, access the video resolution configuration from the Control Panel. Set it back to something surely working, in your case 1024x768, and work it up from there.

Hello my friend,
This can happen when the plug is broken or VGA card is faulty.
first, i suggest to test the screen on another computer: if it works correctly, then you will need to change the VGA card but if it doesn't work i will say that the Screen is defective and need an RMA.
Best Regards,