This may be because the school did not issue you a 1098-T or amounts differ on your return from what is on the 1098-T they did issue you.
Eligible educational institutions file this form for each student they enroll and for whom a reportable transaction is made.
Insurers file this form for each individual to whom they made reimbursements or refunds of qualified tuition and related expenses.
Contact them as soon as possible and find out what their specific issue is with your return. Ask them what you need to provide as proof.