If you have read some of the posts you'll see people think power supply is always faulty.
NOT SO FAST

If you are handy with a voltage tester then you'll really find out. Unplug all power supply connectors to the board and devices.Then plug supply into outlet and be careful not to let each pin connector touch anything.

Find your power supply spec sheet. Find the power output data showing voltages at the 20/24 pin connector. I'll attach a random one here for comparison. If that checks out check the others.

If you are not capable don't attempt. Do at your own risk. But this saved me time and money doing this first. And my supply was fine.