How to fix this issue, if the monitor won’t start even if the PC is running, the lights are on and the fans are rotating?
First of all, check the cables if they are properly plugged on the back of the monitor and on the video card output.
Do a test by connecting the PC to another monitor and with a different cable. Do this in case you have a second monitor and an extra cable.
If not, here is what you can do.
Check if the RAM memory is correctly inserted into the sockets, check if the video card is also correctly inserted into the PCI socket.
The second thing that you can do is to reset the BIOS (CMOS). If you have the manual of the motherboard, search for the jumper that can reset the CMOS.
If you don’t have the motherboard manual, search for the battery, a jumper should be around it. If there is no jumper, search for the other jumpers that are placed on the motherboard.
The CMOS reset jumper should have one free pin and two being occupied. It should also have a marking near it that is saying “JSCMOS” or something like this. Take the jumper out and insert it into “the middle pin and the pin from the other side (that was free)”, and wait around 10 seconds. Remove it again and insert it into the default pins.
Try to start the PC again, it should display the BIOS now.
IF neither of these solutions work, try to replace PC components, start with the video card, the power source and so on.