Windows Activation in Amazon EC2

I'm trying to activate Windows 2008 Server in Amazon EC2 as described here:
https://forums.aws.amazon.com/message.jspa?messageID=185874#185874

I'm trying these two amazon addresses, for my server's region:

ec2-174-129-233-152.compute-1.amazonaws.com
ec2-174-129-233-141.compute-1.amazonaws.com

I get success when I run: slmgr.vbs /skms ec2-174-129-233-152.compute-1.amazonaws.com

The I get a 0xC004F039 error upon running: slmgr.vbs /ato

slmgr.vbs /dli shows:

Registered KMS machine name: ec2-174-129-233-152.compute-1.amazonaws.com:1688

I can't ping:

ec2-174-129-233-152.compute-1.amazonaws.com
ec2-174-129-233-152.compute-1.amazonaws.com:1688
174.129.233.152
14.129.233.152:1688

But I can ping google.com

The time is synced to a server which can activate without any problems, so incorrect request timestamp shouldn't be an issue.

Any help or insight would be much appreciated.

Are you running a local DNS server?

I found that even if you tell IPv4 to use DHCP for its DNS server, Windows will prefer the IPv6 server on ::1. Check by running 'nslookup'.

After making that change, I changed the EC2WindowsActivate plugin and restarted the service, and it activated correctly.