Why is there no signal?

Question

Computers

The computer does not start. A button is pressed, the power supply is working (the blades are spinning), the processor cooler is also working, but it says on the monitor screen that there is no signal, what could be the problem? Components are new.
The components were assembled without a case, just to see if it works. But there is no signal. Connected via vga and hdmi wires.

Answer 1

The problem is solved, it turns out that one bar of RAM is not working.

Answer 2

1. broken video cable
2. vidos died
3. unsuccessful BIOS firmware
and what else is unlikely from your words, because it’s new, but it’s worth checking