Instructors not able to edit course curriculum

My instructors are not able to edit their course curriculum. They were able to before but now when they click edit course and then click on the curriculum tab nothing appears there. I have tried multiple browsers, updating the browsers, clearing the cache. These fixed the issue in the past but are no longer resolving the issue. To be clear when notin editing mode you can see the curriculum , it just does not appear when trying to edit.

The page I need help with: [log in to see the link]