Why do the lectures have no sound in the app?
Edited
Here are reasons why you may be experiencing no sound in the app or when using the Learning Center website while on a mobile device or tablet. Please check the following:
If the device is on silent/muted, the ringer is disabled, or if the lever on the side of your device is switched off, the sound on the app will only work with headphones on
If Bluetooth/Airplay on the devices is connected to another speaker, the sound will not play through your device