Can't take next level - greyed out
I've completed the lessons in the row, but can't advance to the next lesson. Also sometimes I finish a lesson, but when I log in again it hasn't logged it and I have to complete it again.
My tablet does that if I lose connection. It seems to remember all the questions in a lesson and how to mark them but then it doesn't count because I was offline.
I think the same thing has been happening to me with my laptop. My wifi connection has been spotty, and twice, after finishing a lesson with full hearts, I had to log back in.