I have the same issue when using the web browser version, it will work the first time and the voice is talking, but once I close it out and come back voice it not working and some info in the voice bubble is gone.
It works completely fine on my iPhone app, so there is an issue with it on web browsers. I am using Firefox.
I'm experiencing the same problem. Up until a couple of days ago, it seemed to be working. Now there's no voice coach on either my laptop or my Kindle Fire. If you're going to introduce a feature that everyone seems to like, make sure it's a fully functioning feature, not just a teaser.