Over the last few Insider builds of Windows 10 Mobile, many users with higher spec'd phones saw the return of Hey Cortana – the hands-free, voice-activated personal assistant. However, for many users, including on our Lumia 1520 we had the feature but could not get it to recognize our voice during training.
We now have a fix in place the returns the full Hey Cortana feature to build 10586 of Windows 10 Mobile. Remember, only phones with a Snapdragon 800 and higher processor can use the feature as it is hardware dependent.
Here is how to fix Hey Cortana if the training does not recognize your voice. The solution takes no more than a few minutes.
Fix Hey Cortana on Lumia 1520 and Lumia 930
Go into Settings > Time & language > Language
Use the + Add Languages function to add English (United Kingdom). Hit the checkmark at the bottom and yes to the download prompt.
On the main Languages page long press on English (United States) and choose Remove. Now, select the Restart phone button and let the phone reboot