Hi Scarlett,
the button is “pinked” when you’re streaming the lessons - that means in that moment you have to have a fully working internet connection and be logged in to the app correctly.
If you download the lessons, instead, they’re always available on your phone and work also when there’s no internet connection.
Here a few hints with helpful screenshots about how to download. Have a look and let us know if you managed!
Click here to see it: App issue