iMac won’t start back up after being unplugged

If computer gets unplugged/turns off it won’t start back up at all until maybe a couple days later on it’s own. I’ve opened it up, and there are no LED lights on the motherboard while power cable is plugged in and I press the power button.

Power cord has continuity through the hot, neutral and ground.

The Macs AC input port has continuity to the power supply through both wires. I’m thinking faulty PSU?

could it be something else?