Are you setting up a new course? Imagine your Canvas course is like a house. Publishing the course just opens the front door. In this analogy, the modules are rooms. If the modules are "unpublished," then the doors to the rooms are closed. You need to "publish" the module to open the door.
I put all of the content of my courses into my modules, I don't have assignments, quizzes, discussions, pages, or files show up on the students' course navigation bar. So, now, once the module is published, you need to make sure that the items inside the module are also published. In our analogy, publishing the items is akin to opening up a closet door or a dresser.
One mistake that instructors commonly make is to the publish the quiz or assignment, but not the module containing it. That would be akin to opening up a dresser drawer inside a closed bedroom. You've got to publish the module first.
