I've been struggling with this computer for a while. I'm very comfortable with software, but hardware is not my strong suit.
The motherboard used here is an Asus TUF GAMING B560M-PLUS WIFI. I just realized that I had failed to plug in the second power input. Here's a picture of the motherboard components, with the two power inputs highlighted:
Again, I had connected the power input marked as number 1 here, but not the one marked as number 2.
If only number 1 is connected, the computer starts, but there are absolutely no graphics from the CPU through the motherboard. Yes, the CPU supports graphics.
If both are connected, the computer does not start at all. The motherboard lights up somewhere, showing that the power supply works. But, unlike when only power input number 1 is present, the fan doesn't start and the "Power" button on the case doesn't light up after it's pressed.
There is a PC speaker on the motherboard. It beeps if there no memory DIMMs present, by which I mean it does beep when some errors are detected. It does not beep when that second power input is added.
What could this mean?