Have you had to remove one of your course modules due to lack of time? In order to hide both the module and all of its content from your students you will need to:

1. Unpublish the module itself
    
2. Unpublish every item within that particular module

The quickest way to Unpublish both is by clicking the green check mark to the right of the module title and selecting the Unpublish module and all items option.

Unpublishing just the module will block access from individual module items, but if you do not Unpublish the individual items in the module, then those items will still display on the course calendar, the course "To-do" list, the Gradebook, the Assignments page, and the Assignments list at the bottom of the Syllabus page. This means that your students will see that these items are due, but will be unable to access these assignments. To prevent this issue, Unpublish unused material or move assessments to another Published module.

Further Resources:

How do I publish or unpublish a module as an instructor?