A user added a heater underneath a desk, row an external monitor not working.

The technician should ensure that a VGA cable is connected properly between the monitor and the computer. A VGA cable is a type of video cable that carries analog signals. If the cable is loose, damaged, or not plugged in correctly, it can cause the monitor to not display any image or show distorted colors. According to the CompTIA Core1 objectives, one of the common display issues is no image on screen. A troubleshooting guide for monitors also recommends checking the VGA cable connection as a possible solution for no signal or blank screen problems.