I can't hear any/part of sounds on the lessons.
Please check your device as follows.
- Is the volume level set properly?
- Is your headphone connected to your device properly?
- Delete your browser cache (browser history) and try again. You can check how to delete cache from your browser's 'Help'.
- Make sure if the silent mode is disabled if you are studying without headphones.
- Remove downloaded file from the setting menu (gear icon on the top right) and try again.