Make the loop active
When you come to the teacher panel the loop is still Private, only you can see it. The purpose here is that you are able to prepare everything, start your lesson and, at the precise moment you want to, choose to activate the loop. Once you have done that, your students can enter it and start their work. It is not until it says “Active” in the position indicator of the loop that it is active for your students. Naturally, you can prepare everything and activate the loop in advance if you don’t mind your students peeking at the loop before the lesson.