I have been scratching my head for a fix for Cortana who wasn't responding to my voice commands nor my "Hi Cortana" greeting, and finally I got a fix for Windows 10.

Here is how I did it.

  1. Right click the speaker tray icon
  2. Select recoding devices
  3. Select the microphone
  4. Select enhancements
  5. deselect the "Disable all sound effects"

Cortana then worked fine after this tweak. Hope it helps.