CPU fan doesn’t stay on > no display

I’ve just upgraded my PC of 6 years, I’m replacing my RX 480 with a RTX 4070 Super and my Ryzen 7 2700X with a Ryzen 9 5900X so I’ve coped a new PSU, 650W.

Everything is in and I’ve connected all the wires as I had before. On launch the CPU fan spins and then stops abruptly, if I plug the fan into another fan output, it works fine, so surely the fan isn’t broken.

I have reseated my CPU and checked for bent pins, no signs that anything shouldn’t work. I’m not getting any display even when using my motherboard (ASUS B450 Prime) display output.

PC part picker said there may be an issue with my BIOS but I wouldn’t know where to start with updating that, especially if I’m not getting any display to work off.

Any suggestions? I may not have included everything needed to diagnose

ignore the unmasterful dust