No power at all

I have an Xbox series x that just turned off while watching Netflix. It has no power at all when the button is pressed.

I have tried a different power cable and different sockets still the same. I can hear a crack of electricity when the power cable is plugged in so the PSU seems ok on that side.

I watched a YouTube video about PSU issues and have stripped it down and tested the PSU which has output voltage of just under 12v on both cables so this seems good.

I did a continuity test on the power connection on the main board and the smaller board and didn't get anything back so I assume nothing has shorted out.

Does anyone have any ideas? As I am at about the limit of my skill set for fault finding the issue.