Student loan

I am the surety on a student loan for which my sister app****. She app**** for a loan in her first and second year and was applying for a loan for her third year. The application was done and the loan declined due to credit checks not met. The branch consultants helped me obtain a full credit report and also scrutinized thr report but could not identify any instances as to why my credit record would not be sufficient. The branch then assited in phoning general inquiries since the student loan department does not have a direct contact number, however the general inquiries indicated thay they could not disclose/access this information. They adviced me on 3 January 2019 to email the student loan arbitration department which is supposed to respond within 48hours. However no response has been received.