Nothing connecting to pc.

Registration date
Monday February 22, 2021
Last seen
February 22, 2021
So i just built a pc using some older parts, it turns on fine, fans are on, lights are on, everything is good. but i plugged a monitor into it and it continued to display "no signal" made sure it wasnt the monitor, and even when i plugged in my keyboard and mouse, no lights went on at all.

If anyone can help i will love your face, same thing happened with my old pc, couldnt find out what was wrong and decided to put some money together and just build a new one, instead of using the old hand me down.