In the Learning Lab: Introduction to GitHub, in Step 2 “Turn On GitHub Pages”, there is a bug that makes the students get stuck:
If the student selects a Theme, the following error occurs:
And it is no longer possible to continue with the course.
However, we found a workaround, which is to Save the Source to None (to disable GitHub Pages) and Save. Then select again the Master branch and saving AND not selecting a Theme.