To move on to the next unit, you must first complete all of the lessons in the previous unit. You can tell if you are missing something by looking for the green checkmark next to the assignment.
If you notice that you are missing a checkmark, please revisit that assignment and complete any tasks required. Oftentimes, these are ungraded assignments, and you only need to spend a few seconds on the page for it to count as completed and earn the green checkmark.
If all of your assignments show as completed, but you are still unable to continue, please reply and let us know.
Thanks