The default ePub organization is by module, meaning only items that students have access to view in each module will be included in the ePub file. Locked modules list either their pre-requisites or the unlock date, as well as the items that are contained within that module (though not the actual content of those items themselves).
If you do not want the ePub file to be organized by Modules, you can choose to set your course organization by content type (e.g. assignments, quizzes, etc.).
ePub Exporting is currently a course opt-in feature. To enable this feature, learn how to manage feature previews in the course features lesson.
If your account does not display the ePub Export option, your institution may only allow you to manage offline content as an HTML file. The offline content feature will override the ePub Exporting feature preview, as both features cannot be used together.
In Course Navigation, click the Settings link.
Open Course Details
Click the Course Details tab.
Organize ePub by Content Type
In the Course Details tab, locate the ePub Export section. Click the Organize ePub by content type checkbox.