1. Send an email to the school or go directly to the student center to apply to the department to rebuild GC. I don't know how many opportunities to rebuild GC need to be discussed with the school, depending on the school.

Since you haven't reached the mark required by the Master of Sydney University, consider transferring. If the average score meets the requirements of non-Eighth National Congress, you can transfer to other schools, such as UTS in Sydney (depending on how many points you scored, send them to the school to try to see if they meet the admission requirements).