1. The computer doesn't respond at all. It may be that the power supply is not connected properly. Just check the patch panel and chassis plug, and then plug it in again.
2. Also, the computer case has been turned on, but the display screen is still black. In this case, it is possible that the power supply of the display screen is not connected properly or there is a problem with the connector connected to the computer chassis, so it is necessary to check whether the power supply is connected properly and whether the display screen and the computer host are connected normally.
3. There is something wrong with the motherboard wiring, which needs to be sent to a computer repair shop for professional repair.
4. It is caused by poor contact between the gold finger of the memory or graphics card and the motherboard, so it is necessary to unplug the memory and graphics card, clean up the gold finger and reinstall it.
Another possibility is that the computer is infected with Trojan virus, and the computer can't start normally. In this case, you can go to the computer repair center for repair.
6. It may be that there is something wrong with the wire or power supply, and it may be damaged by rats or other circumstances. In this case, just check the wiring and replace it if there is any problem.