Question RGB lights on CPU cooler turn on but PC won’t power on

[Wimpy Mike]

To give the full story I’ve built this PC around December 2023 and it’s been lying around until now. The PC worked fine at that time and it would power on without trouble. However, fast forward a year later, it won’t power on despite the some of the RGB lighting up when switching the PS on. The only modification I made was adding a hard drive from an old pc to this pc, but even without it plugged in, it still won’t power on (The OS is on the SSD). Weird thing is after several times switching the PS and case power button on and off it would sometimes work. I’m ruling it out to be related with the MB or PS but I’m not very experienced with computers so I’m hoping someone could provide the solution or pin point the problem and suggest how I could fix/troubleshoot this. I’m more than happy to provide any information so feel free to ask. Thank you!

Here are the specs:
mb: AORUS Z690 ULTRA
gpu: AORUS RTX 3090 XTREME
cpu: i9-12900K
ssd: SN850X NVMe SSD 1 tb
ram: AORUS DDR5 5200MHz 2x16GB
ps: Seasonic FOCUS PX-850 +80 PLAT

PS switched on:

https://imgur.com/a/m7Gqldw

View: https://imgur.com/a/m7Gqldw


I’ve also tried pushing the power switch (red button) and nothing happens.

 

[Hellfire13]

Sometimes, when a PSU stays connected to other components but not used for a prolonged period of time, it can develop something which can be called as idle fault. This is not guaranteed though and cannot be replicated, as it varies from device to device. It generally happens due to bad caps degrading over time, more than anything else.
Although that PSU is very good quality and its very unlikely but it sounds something similar. Try cleaning out the connectors and reconnecting everything from scratch.