Monitor issue??

A couple weeks ago, my monitor began faintly but rapidly flashing, and eventually the screen went black. Not off, no messages, just black. Upon toggling the power switch off then back on, the monitor would work for less than 2 seconds, then go black again. For awhile, rebooting did the trick for a length of time, but the monitor would always go back off. Eventually the rebooting stopped working altogether. Now it will flash for -2 seconds and remain black upon reboot.

Things I've tried-
Separate cable
separate power cord
different monitor (this monitor said it could find no signal) and a combination of this and all cables- display remained dark on this as well
removed the graphics card and used original port
4 separate outlets
new power strips

I even bought A NEW COMPUTER and tried all of the above AGAIN with the above!!! (and again, with the other monitor, it says "no signal".) I am so stupefied, upset, and desperate. I really hope someone has an idea. There was no prompting it, just during regular use it randomly started happening.

Thanks in advance to anyone who helps!