If you are trying to use the new ‘Hey Cortana’ feature and it is not working, you should watch the video below.
This feature is turned off by default and you need to enable it so you can begin to use Microsoft’s personal digital assistant.
To enable ‘Hey Cortana’, open Cortana and click the icon or button in the top left of the window and go to settings. At the bottom of the window, you will see the ‘Hey Cortana’ setting that you need to enable.
After you enable this feature, you can begin to freely talk to Cortana.
Here’s a video that shows the process.