Hi @joseph_dixon and welcome to the Canvas Community! That is normally the message that appears when a student tries to access a content page, but that page has not been published. This page contains information about publishing a page, How do I create a new page in a course?, so could be useful in your situation.
It is likely that after the page is published, students will no longer receive this error message, but if something still isn't working correctly, please let us know!
We also see this quite a lot when people have copied and pasted links from one site into another instead of using the import content tool. Running the link checker identifies links that go to other Canvas course sites which students probably can't access.
I decided to give up on linking my Canvas Syllabus straight to Google Docs from by Canvas my home page. I created a Canvas "PAGE" containing a calendar with links to assignments and notes. It's working fine and the students find it easier to navigate.