Tested PSU with detection tool, no fan spin, just a single clicking noise, eco mode off and toggled, no fan spin at all.

Systom
Tested PSU with detection tool, no fan spin, just a single clicking noise, eco mode off and toggled, no fan spin at all.

Doesn't sound good.

Update:
New motherboard received, other components tested, CPU/RAM/M2/GPU/AIO, all working fine. Phew.
I sent the PSU along with the 24 pin cable to EVGA a couple of days ago, will report back once they receive it and determine if anything is wrong or not.

That is Good News

UPDATE: Finally received what appears to be a replacement/refurbished unit. Yes, the serials different.
Except I can't use it because they didn't send the 24pin cable back with it...
Contacted EVGA yet again, and once again, they're gonna send that cable back out to me.
I know they state not to send cables with but if it's potentially the problem or a part of it?
To be fair as well, I put a giant worded note at the top of the box stating this...

thanks for the update

The RMA receiving department may be separate from the RMA shipping department, so it may not have made it from one tech to the second.

EVGA typically doesn’t return the same unit when an RMA is completed either, unless the unit was damaged by the user. As long as the user didn’t damage the product, it gets replaced.

Hopefully everything is good once you get it all installed.

I might buy PSU tester before you try the 24pin connecter. I had to RMA my Supernova G3 550. Out of the box plugged it into to my good mobo and immediately began to smell burning. It was subtle so I thought it was just current heating up some plastic in the connectors. After the board didn't post I unplugged the cables and tried an old dell PSU I knew worked with that mobo. After that it wouldn't even power up with the old PSU. Still not sure what was at fault doing troubleshooting I plugged it into my Dell mobo and that was much more dramatic. As soon as I switched it on a puff of smoke came up from the mobo and a strong smell of smoke. I bought a thermaltake Dr Power II and tested the PSU which it failed the tests. I got my replacement mobo and a interim PSU lent to me from a friend and it turns out all 4 of my HDs that were connected when the mobo fried wouldn't spin up anymore which is from HD PCB damage usually. Last week they said the PSU tested good but they still shipped out a new G3 650 to me. I got the PSU today and the PSU and all cables tested good. I went and tested the old cables and the old 24 pin mobo cable failed on the tester.