PSU operation help

Right, I have fitted an Abit AN8 ultra in my gigabyte aurora case with a x850 pro, and it wont start, 5vsb light is on on the mobo, but press the power switch and ..no fans nothing.

I read on the Abit forum of something similar happening to somebody in an older tower case, the switch voltage went to earth via the front panel circuit board and it wouldn't switch on (TBH the post wasn' very clear!)

The switch on my case is just two wires, so as far as I can see it cannot have any connection to a common earth.

My psu is an Aerocool2 (420 or 450 W ) and I have a vague recollection of mbm5 having a problem with it when I put it in due to the apparent lack of a "-5v". I asked on the forums then and recieved the reply that it wasn't a problem as my NF7-S didn't need one.

Is this correct and could this cause my "non starting" problem.

Please help! as I am already well beyond the limit of my knowledge and reaching the end of my patience!

(Sorry this is a bit "war & peace!)

Did you ask this somewhere else? I seem to recall replying to it, but anway, short the pins on the mobo with (for eg) a screwdriver, see if it starts, if it doesnt short the green wire to the black wire (any will do) on the psu connector. If the psu doesnt start up then you have a duff psu.

I have since put my old msi neo2 system back together, and that works fine so the psu works it is just if this board requires a -5v and the msi doesn't

The only thing the -5 is required for is ISA cards and some sound systems. Would seem to be a duff mobo then.