Microsoft Server Volume Licensing Question

I hate Microsoft Licensing so here it is... I have a Physical Server with Dual Quad Cores that is licensed with our Volume License Key (I believe it was two 16 Core License Packs attached to the license key). If I'm not mistaken we are licensed for two virtual guests on this one physical host. This hyper-v host has one virtual Domain Controller guest (Licensed) on it (no other guests).

We installed one additional virtual Guest (this brings the count to Two Virtual Guests). The New Guest is not taking the license key and throwing an error. According to the error we are out of Activations for the key which is why it can't be activated.

I came from server 2003 era where one license per OS install where just a handful of Volume license keys were used and it came down to activations per license key. So the question now is How many licenses do I need to buy for my second virtual Guest Machine? Also we get our licenses through Tech Soup and often times they seem to just "re-Arm" the existing Volume license key and in some cases send us a new unique one so I'm not certain what should really be happening as i'm not certain I can see the "Activations" similar to how an Office Product Key works.