Some activities like choice, database, workshop or quiz have some time or phase restrictions, so the student is not able to do nothing until the activity opens or change the phase (usually teacher decision).

Right now, we don't allow to prefetch/download this activities to work offline because we think the user is not able to do anything.

Nevertheless, when the user enters the activity in offline mode, it shows an error: "you are not connected to the network...blabla".

It's a UX decision to think if we're acting the right way or if it's better to allow users to prefetch the activity so the reason why the activity cannot be done at that moment is cached.