When i try to turn on my newly built pc the fan's light flickers for a second and it doesn't power on. I verified that this wasn't my psu with a youtube video. There aren't any beeps or anything.
Check all the power connections are secure, if no joy unplug power from all but the motherboard plugs 20+4 and the 4/8 by the CPU, and the Video card , if still no joy, let us know CPU, mobo, GPU, PSU, etc
It could be inadequate or too much thermal paste. Too much will not allow heat transfer to the heatsink, inadquate will not give proper transfer of heat causing the cput o overheat and shut down.