500R Case front USB3 ports issue

The left port on the case as I'm looking at it doesn't function at all when any USB devices are connected. I've tries with USB3 and USB2 flash drives and external HDD but no joy. The port next to it works OK (Right Side) with all my external USB devices.



The 20pin connector is seated correctly to my ASUS SABERTOOTH 990FX mainboard.



Any suggestions or is it just faulty?