|I myself own a NZXT tower (not the gurdian) and have built many machines with NZXT cases. |
It would probably be best to bench test your machine even though you confirmed that it is working, it is good practice now that you are having problems.
This will also give you the chance to look behind the motherboard to see if you have a stray screw fallen behind shorting the board, which is not uncommon.
if you do not want to take the board out then, unplug all uneccessay thing such as case fans, additional hard drives etc from the board, keep only the cpu, one ram stick, one hard drive and GPU. i would unplug all the cables from the PSU and reinstall them from scratch.
in terms of the internal wiring, for the power switch you just need to ensure you jump the correct two pins on the board, polarity is not an issue for the power switch. To eliminate the switch itself you can short the two pins (carefully0 with a plastic handle screw driver.
To be honets there are loads of things you can do to test what is going wrong, but i think maybe the above is a good starting point.