Error: 0xC004F074 The Software Licensing Service reported that the computer could not be activated. The Key Management Service (KMS) is unavailable.
I recall having done this a long time ago and searching around I found some old correspondence from back in 2011 with Amazon Support that involved activating with the external IP of their KMS servers. However this was what was giving me that error. Unfortunately, I did not make good notes of that so I was going to have to figure out again. Fortunately, Internet to the rescue, I found this: http://kwjblogs.blogspot.ca/2012/01/amazon-ec2-instance-windows-activation.html
... and recalled essentially doing this:
slmgr.vbs /skms 169.254.169.250
Done. Now I also have noted it.