If you get a message telling you to "Try connecting to wifi and download the workout for offline use.", it means that an update to your phone has caused some issues to the app. This is easily resolved by deleting the app and then reinstalling and logging in. We are sorry you have to go to the trouble, but it fixes the issue quickly.
Download Workouts
If you haven't downloaded your workouts yet, you should do that. It will prevent them from needing to be streamed, and provide uninterrupted play.
Click on the cloud icon next to the workout (yellow)
When downloaded, it will be checked (green)