Cortana Helper Tool is a freeware that will restore & reset all Cortana settings in Windows 10.

It basically:
  1. Restore Cortana Settings to default values
  2. Fixes Cortana is disabled by company policy issue
  3. Fixes Online Search is disabled by company policy issue
  4. Customizes Cortana and Windows Search Functionalities.

Go get it here.

See this post if Taskbar Search & Cortana is not working.