I have recently been on a project rolling out Windows 10 to a client. A problem that we faced after building our Windows 10 image was the search function not working - or Cortana Search!
Our environment was setup with 2K12R2 servers and a WDS setup with unattend XMLs for configuration.
Everything went well until we tried searching after imaging a whole lab of machines... What a mistake that was.. Luckily after some Googlefu and urgent searching a result showed up for unattend XMLs and Cortana Search not working.
Long story short, don't use the CopyProfile parameter in your unattend XMLs as this somehow breaks the Cortana Search app and stops your search from working!
Good luck out there!
TLDR; Don't use the CopyProfile switch in your unattend XMLs. This breaks Cortana Search, only fix is to re-image the machine.