For undergraduates, the PLUS loan is a loan that is given to a parent of a dependent student, not to the student. If someone was denied the loan, it was one of your parents, not you. The issue may be that you will no longer be a dependent student once you turn 24. The rules are not set by the school’s financial aid office; the PLUS loan is federal loan and the school must administer the program according to federal regulations.
Basic information is available here: