My computer turns on but no display :(

Hello so>
recently my computer started blue screening, in process of repairing it (it was a software issue to do with windows updates) i broke the fan on the heat sink, was a stupid mistake i know :(. i replaced my heat sink with a new one i bought, now the computer wont start up.
When the computer turns on normally i will hear 1 beep and it runs perfectly fine with the power button led lights showing up green.
The LED lights will not turn on and i don't hear a beep.
GPU + Powersupply was replaced recently to a Corsair Vs550, Gpu is Nivida gtx960
i have redone all plugs (mother board etc) tried running with GPU out, Ram out. (replace after take out and try the next thing)
the computer will turn on the fans will work the lights inside but still no display ( or front panel led lights and the single beep)
It was working fine the day before i replaced my heat sink could this be it?
Any feed back will be greatly appreciated.