Thanks Mary. I have logged in as a real student and I can see it.
What seriously worried me is this:
When I switch to student view in my practice course from the Moodle MOOC, I can see the "Add submission" button and I assumed that I should be able to see it in other courses as well.
But I could not see it in my real course that I have just created. I assumed I had done something different/wrong.
Why can I see it in the MOOC practice course but not in other courses?
with thanks
Marilyn