suddenly can't add people

Community Novice

Starting yesterday afternoon I suddenly can no longer add people to my course in the free for teachers version. It gives me an error message saying, "We were unable to find matches below". I've always been able to add someone's email address in the add people function and it would send them an email to access the course. The only thing I can find that looks like it might have changed is the "Visibility" in Settings. It now says to contact my administrator/support to make public. But who is my admin/support if I have the free for teacher version? Why did this change? How do I fix it? Help!