Both the monitor and computer need to first be independently verified on another known good monitor and computer to localize the problem to one device or the other. Then troubleshooting can begin on the problem device.
Some common computer scenarios that can result in this symptom:
- Bad video card or motherboard.
- Bad power supply.
- Other bad component device resulting in POST not completing.
- Memory modules that need to be reseated to improve electrical connectivity - often happens after computer is moved or transported.