What should I do if my new PC won’t turn on after building it?

I faced the same issue when I built my PC. What fixed it for me was reconnecting the JFP1 header to the correct pins on the motherboard—worth double-checking!

It’s important to clarify what you mean by "doesn't power on". If nothing happens at all, you might have forgotten to flip the PSU switch. If fans or LEDs light up but you get no display, it’s a common mistake to connect the monitor to the motherboard instead of the GPU. Also, check your motherboard for any status lights or error indicators and consult the manual for troubleshooting steps.

First things first, check the switch on the back of your power supply to ensure it's set to the 'on' position. If it's plugged into a power strip, double-check that too. Make sure you turned on your monitor and reseat the HDMI cable. Also, take a look at all the cables from your PSU and make sure they're properly connected. If you have integrated graphics, try plugging the HDMI directly into the motherboard instead of your GPU; this way, we can rule out the graphics card as the problem.

Make sure the motherboard connector is fully plugged in. Modern power supplies usually need a load to turn on properly, so if it's not seated completely, it won't power on. You might need to push pretty hard to get the clip engaged.

It would be useful to know more about your build and what LEDs are lighting up on your motherboard. It could be a connection issue, a BIOS update needed, or RAM not seated correctly. More details can help us figure this out!