RUN button disappearing


Hi there, I keep running into this problem: when a new step loads, sometimes there is no "RUN" button at the bottom of the page so I cannot submit my code and go to the next task. Perhaps I am missing something obvious here? I have refreshed the page but it didn't help. I work with Mozilla browser (any other browser is not available at work).
Has anyone experienced this?


I find it reappears again if I expand and contract the internal browser window on the right.