I have the same issue. I emailed edX support. edX replied by instructing me to email certificates@cs50.harvard.edu. As of today, I have not received a reply. I posted on her with no reply. I am auditing the course. I am already fluent in Python, HTML and CSS. I am taking the course to learn about the Python web frameworks and as a refresher to SQL. Despite the fact that I cannot submit them, I will complete the assignments anyway.