So all of a sudden i lost all audio/voice prompts and after troubleshooting my phone and Fenix 3 HR, I finally figured out it was the latest update of Garmin Connect (android) that did it.
I've rolled back to a previous version and the prompts work perfectly. Tested by updating again and even doing a clean install but the prompts still get broken.
So until they fix it, roll back to get your prompts working again. I've emailed support but no response yet.