A graded assignment in your course may show as ‘Due’ or not be marked as ‘Completed’ if you are missing a green check mark in that section, but this does not affect your grading or certificate status. Sometimes advanced assignment types might not receive the green check mark.
You can read more about missing green check marks in this article.
Your scores and your eligibility for the certificate are determined by the points you earn on graded assessments as reflected on your Progress page. You can qualify for the certificate as long as you earn a passing score before the course ends. A missing check mark will not adversely affect your score.