https://community.logos.com/forums/t/197834.aspx
Although the HB091 Listen and Learn interactive works properly on the desktop and the web app, it returns an error when tapping the interactive on iPadOS:
"Error Loading Book
This resource cannot be opened because it is not part of your library."

I downloaded the HB091 course (but not its video or audio multimedia) to see if that would clear up the issue, but the interactive still does not work.
The error message seems a bit misleading, since the resource is a part of my library (and does appear in the Library on the mobile app).
9.1.1 (0011) on iPadOS 14.2 (18B92)