No sound on Lessons & Songs App

I just installed the Lessons & Songs App on my IPhone. The App appears to be working and displaying the progress on both the Iphone and my laptop, except no sound on either the IPhone or on the laptop.
Suggestions?

I’ve occasionally seen the App fail to produce sound, after I’ve just used another audio app such as Spotify, or when screen sharing to a Smart TV.

Suggest you restart your device. If that doesn’t help, re-install the app. All your settings and lesson progress will be preserved.