Hi @JodyCull,
Are both the course and whatever you're trying to view inside of it (assignment/quiz/page/fileetc) published? As the view as student feature checks for all of the things a real student account would, you won't be generally able to see unpublished content (or content in an unpublished course, except maybe the home page for some reason). Also, make sure the content you're viewing is in the course, as you'd get a similar message if, for example, you have an image from another course embedded on a page. If you're the teacher of the other course, you have access to the image so it would work for you, but in student view, you only have the access to the one course you're working in, so would all of a sudden see an error.
Let us know if this info helps solve the issue or not!
-Chris
