I just built a PC for my brother today, and there seems to be a power issue. When I turn it on, the motherboard lights turn on for a second, and the GPU fans spin, but they both stop immediately. The RAM lights up, and stays lit up while it's on. None of the case fans are working, and the CPU fan isn't working, nor is it lit up (I'm using a 3700x with the stock cooler). I've tested this with the CPU power header unplugged, and the exact same result happens, which leads me to think that my CPU isn't receiving power. I have no idea what the issue could be though. My power supply seems to be functional based on the fact that the PC is able to power on. I'm using a semi modular PSU from seasonic. None of the cables were labeled, but there were two four pin connectors which I'm assuming were for the CPU power header. If anyone knows what the issue could be then please let me know. I'm still relatively new to PC building, and this is actually the first time I've built one myself