Depending on the assignment type and the situation, your course staff may be able to provide a short extension for individual assignments. Please reach out to your course team directly with any contact information they provide within the course, or post on the course discussion forum.
It is certainly possible to pass an edX course if you miss some assignments; however, coursework is progressive, so you should review and study what you may have missed.
Some courses automatically drop one or more of your lowest graded assignments. Check your course syllabus for important dates and more information.