Windows 8.1 AD Based Activation “Invalid product key or license mismatch” error

I was trying to add Windows 8.1 Key to Active Directory that day using Volume Activation Management Tool (VAMT) to enable AD based activation,  and i get the “Invalid product key or license mismatch”error when trying to add the Windows 8.1 KMS key using AD based activation.

Doing a quick search, i found this hot fix from Microsoft under the title of (Update adds support for Windows 8.1 and Windows Server 2012 R2 clients to Windows Server 2008, Windows 7, Windows Server 2008 R2, Windows 8, and Windows Server 2012 KMS hosts). Installing the fix on the server where VAMT is installed solves the issue and saves the day!