Hello!
Unfortunately, Penn Foster allows only 30 days to retake an exam due to the accreditation rules the school must follow. After the 30 days, too much time has passed to retake the exam and the original grade is taken as the final grade. The "View Exam Results" button will also now include the answers to any questions you got wrong (if applicable), so you will know for subsequent exams.
The minimum passing average for a course subject is 65. As long as your average for a certain subject is above this grade overall, you will pass the course. If you believe you are at risk of failing a course or have failed a course, you can give the school a call at 1-888-427-1000 (Hours: Mon-Fri, 9 AM - 6 PM Eastern Time) to speak with the instructors.