You may get the following error while activating Windows 2008 R2 ( Error: 0xC004F074)

error 0xC004F074-The Software licencing service reported that the computer could not be activated since the key management service (KMS) was unavailabale

You are probably getting this error because the KMS TCP port 1688 is not enabled or blocked in the firewall. So check your firewall and enable port 1688 to resolve this issue.