Unable to perform an unattended domain join using WDS and an answer file on Windows 8.1

It is a bug in WDS. When you approve a UEFI device it gives the wrong permissions. If you look under the security permissions on the computer object you will see it has set deny for Domain Admins against the 'Change password' and 'Reset password'. Remove the deny for both of these and you are good to go.

You will need to do this for each UEFI computer you approve through WDS but it is better than nothing.

We ended up contacting Microsoft regarding this and after several weeks of useless tests, turns out there is a bug in WDS name and approve and PXE booting when using UEFI over BIOS and unattended domain joining is simply non-functional over UEFI when pxe booting with WDS name and approve.

Long story short, keep using BIOS if you want automated joins with WDS. If you are forced to use UEFI, the only other alternative would be to use a logon script after deployment but this assumes the account that will be logged in is an administrator. Either that or manually join the domain post-deployment!

Hope this helps somebody else with this same problem. I know it caused me some major headaches.

Cheers!

You are still missing either the Credentials setting or the Provisioning setting. See AccountData for how to use UnattendedJoin without entering credentials through Provisioning.