AX760i - no power to board except on self-test.

I came to turn on my computer this morning but there's no power when pressing either the case power button or motherboard power button. Self test with everything disconnected works (fan spins, green light) but when everything is connected it behaves the same way - instead of just a click it powers it's fan and sends power to the rest of the system. Case and H100i fans spin and the power lamp on the board comes on (but not on the case). When the self-test is finished the green light remains on the PSU but still no power when pressing either power button.



The PC has been working fine for a year.



PC specs in drop-down.



Cheers!