Just double check you have the 12v 24 pin main Atx power blocl connected from your PSU.
And that you have connected the eight pin E-atx 12v, or 12v Eps power connector of the Psu to the socket for the power on your motherboard.
That you have also connected the required 12v Pci-e power connectors to the graphics card if fitted to the Pci-e card slot of the motherboard.
Go to the back of the system case, locate the rocker switch on the PSU it`s self.
If it is set to it`s normal operating state, on.
Set it to off.
Turn the switch off at the wall socket from the PSU`s cord.
Pull the plug out and count ten seconds.
Plug it back in, and turn on the switch at the wall socket then return the rocker switch back to the normal power operation setting.
Press the power button on the system and see if it powers up FireBlur.
The PSU may of had one of it`s power protection circuits triggered, and this is how you clear them so the PSU will hopefully power the system up right once cleared of errors.