Ag neovo f-419 lcd monitor problem

a few days ago, i connected my scanner to a usb port in the back of the pc and pressed a key on my usb keyboard to log into windows.

as soon as i pressed the key, the monitor screen turned blank. i turned the monitor off and on again, but it would just flash 'no signal' for a split second and blank out again, with the power light going from green to amber.

since then, i've tried fixing it by pressing the auto-adjust button a few times and leaving the monitor vga and power cables unplugged on both ends overnight.

this morning, i plugged in the power cable again and the problem is still there. can someone please help me out?