The latest server host key I have in the VL service center is Server 2012 and I have found that it won't activate Windows 8.1.

1 – REMOVE ICLOUD ACTIVATION LOCK ON IPHONE OR IPAD, IOS 16.3.1 Supported PassFab's Activation Unlock tool is compatible with all versions of Windows, including Windows 10, 8, 7, and XP.