Computer won’t turn on after installing GTX 1080

[JayTee3]

I installed it and PC won’t turn on... I bought this off gumtree so hopefully it’s not a DOA, but what should I check to know if it’s a DOA or what the problem is? Was working fine before with GTX 1060

I have 6+2 pin in the 8 pin slot and 6 pin in the 6 pin slot so power should be all good. I have a 600 watt PSU.

Help?

 

[JayTee3]

Weird, dunno what happened but just opening it and looking through and pushing down some cables seemed to work. Weird, a cable must of just been loose or something.