Question GPU wont let my computer turn on?

[amco_krkic]

So ive just cleaned my motherboard and ive reattached it back on and ive put all the cables back on like the 24 pin and the 8 pin cpu and the front panel connectors but when i tried to power it on it wouldnt. I thought it was because of the front panel connectors and so i took a look and they were all fine, i took a look at the motherboard 24 pin connector and that was also fine, and the cpu connector was fine also, but when i unplug my gpu and turned it on it indeed turned on, when i plugged it back in it wouldnt turn on,
I dont know if this is because of the gpu, the motherboard or the front panel connectors i have plugged in

My specs are,
Motherboard- asus p7h55-m
GPU- sapphire nitro rx 480 8GB
Cpu is intel i5 760 @2.8ghz
Please help!

 

[rgd1101]

and the pcie power to the gpu?
make and model of the psu?

 

[amco_krkic]

The power cable to the gpu is an 8 pin and i just replaced my old power supply a week ago with a win power plus 650W