Having an issue with VT-x not being detected

I've recently built a new machine, planned as a significant upgrade from my last box...

• Gigabyte X99P-SLI Motherboard
• Intel i7-5930K CPU (Intel® Virtualization Technology (VT-x): Yes)
• 64 GB RAM
• Windows 10 Enterprise

I've enabled VT-x and VT-d in the BIOS.

CPU Z Output:

Securable Output:

What am I missing? How can I get Windows to detect virtualisation?

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