If your course progress isn’t saving correctly, please make sure to log out of all other devices you may have used to access the course.
Also, keep in mind that some users accidentally open the Study Guide instead of the actual course. While they look very similar, the key difference is that the course includes quizzes and the final exam, whereas the Study Guide does not.
You can find the Study Guide at the top right corner of the main course page — make sure you’re working in the actual course to ensure your progress is saved.