I recently got a new motherboard because I am pretty sure the current one is a bit dodgy. I built it outside of the case and powered it on, however it turns on, beeps once and then almost immediately shuts off. I know that it isn't a PSU issue, and I am pretty sure it isn't a CPU issue. One thing that is interesting is that when I unplug the CPU 4-pin connector and turn on the PC, it all runs "normally". It should be noted that I don't have the CPU cooler currently installed as it just gets in the way of doing these tests and other cables.
What could this issue be?