Oh, you may have read things before joining the course — way at the beginning, but they may not be checked off?
See in the sidebar it says how many lessons in the module are completed. And at the end of a lesson I’ve scrolled down on the right — there’s the “complete” button.
I’ll double-check settings on the course, it is linear you’ll need to complete the lessons in order but in case you read any of them before actually joining the course, double-check the number of completed lessons and make sure the ones that were available in preview are also completed.
Please let me know if there’s any further troubles! 🙂 I want the course to work as expected.