Credit Criteria not meet

Good day I have app**** for credit from African bank and it was rejected, i have ask for the reason but I was told that I don't meet the criteria. I have ask the lady to advise me what criteria I don't and she advise that she can not tell me. as the is nothing showing from her side. I must log a complain so the it can be investigated, I don't have any adverse on my credit profile and a good credit score. So I would like to know the criteria that i do not meet from Africa bank and it it will help me work it if any. Thanks