This also failed for us but may have been due to not having enough requests to meet the activation threshold (25) on the KMS server.
CSCRIPT "%WINDIR%\system32\slmgr.vbs" /skms yourkmsservername:1688
CSCRIPT "%WINDIR%\system32\slmgr.vbs" /ipk 33PXH-7Y6KF-2VJC9-XBBR8-HVTHH
CSCRIPT "%WINDIR%\system32\slmgr.vbs" /ato
You might also try this on your golden image and then recompose:
The scripts run as the system user. If you use a proxy server, the system user might need to have a proxy specified:
NETSH winhttp SET proxy yourproxyservername:andport
CSCRIPT "%WINDIR%\system32\slmgr.vbs" /skms yourkmsservername:1688
CSCRIPT "%WINDIR%\system32\slmgr.vbs" /ipk 33PXH-7Y6KF-2VJC9-XBBR8-HVTHH
CSCRIPT "%WINDIR%\system32\slmgr.vbs" /ato
NETSH winhttp reset proxy