Why does it show something is incomplete when I have finished it?

The "Incomplete" refers to whether or not you've marked lessons complete in Teachable, which is optional. To mark a lesson complete, click the red "Complete and Continue" button in the upper right corner of a lesson window:

Do note that you can mark a lesson complete without watching the video in that lesson, and you will need to mark lessons you do not need to watch as complete to get a "Complete" notation. 

Tip: You will unlock a course certificate when you have marked all lessons in Design to Shine as complete. Please see this page for more details.