Sometimes a user may see a blue box on the monitor with a message along the lines of "No Signal Detected." All this means is the monitor has no signal. Most of the time, this is not a problem with the monitor, but with the computer or cables in between.
The best thing you can do in this scenario is check any wire that looks like the Image posted below.
If all the wires in the computer and monitor are pushed in screwed in tight, it's time to send a helpdesk ticket. More often than you might think, however, you may have resolved the issue simply by checking the wires.