|All that is needed to post is PSU, MB with HS/fan, CPU, 1 stick RAM, graphics, keyboard, monitor.|
Try disconnecting all case to board wiring, any USB headers to board, drives, extra RAM, etc. Also any external hardware except keyboard.
Be sure the CPU cooler is connected to the header marked CPU fan.
Start the computer by momentarily touching both power switch pins with a screwdriver.
If you can't post with that configuration then the issue is PSU, board, CPU or RAM.
If you have multiple sticks of RAM then try them one by one.
Also try the board outside the case to verify there is no board to case shorting.