@SusanNiemeyer , I can understand how it can be confusing for other instructors, however if you hover over the cross-eyed label it will provide you with a small description about why it's disabled. It will likely either say No Content; Not Visible to Students or Disabled; Not visible to students. In my experience that has solved a lot of the confusion. It's all really how either you or your school has Canvas set-up.
By default, all course navigation links are enabled (unlocked), unless your school sets it up otherwise. However, if all links are enabled and you're still seeing those crossed out eyeballs, it means there's no content yet, and Canvas doesn't bother sharing that link with students until there is something meaningful there for them.
Hope that can provide a little additional information for anyone needing it.