vehicle finance application rejected without valid reason

i was just declined for vehicle finance recently and the reason being Non-Supportive Trade reference, i find this to be very strange the reason being i do have accounts that i am paying every month, i even have a car that is financed by ABSA, my credit score is above 600 which regarded as GOOD by Credit Bureaus, i honestly do not understand the reason for declining my application. Can someone from MFC please explain to me what exactly the is the reason for declining, i need a satisfying reason.