PC will not power on

[Dogoid]

How was it the incorrect 8 pin?

 

[Silicon Si]

How was it the incorrect 8 pin?

With modular psu's you must use the correct cables for that psu as not all makes are wired the same there is a big warning about that in the instructions with my Seasonic psu

 

[Temp.sgk]

So from rereading this topic it would had been easily solved if OP actually tried his old PSU instead of the new one.