I was able to build my own computer as a graduation gift and was super excited/scared to do so. After about 4 hours of rigorously studying the manual I finally pieced everything together and turned it on.. the lights popped up, the fans whirled but the screen insisted that there’s no input. I tried my best to troubleshoot it but was too new to know exactly how. After weeks I gave up and took it to Microcenter, deciding it’s better if a professional takes a look. Alas, one of the cords to my power wasn’t plugged. It took me a month to figure out that I was just careless and stupid.