No specific reason for rejection

After waiting since March to find out if I have been rejected/accepted through CAO portal, just to be told I'm rejected which I don't have a problem with, but , Ihave a problem with the fact that I don't know why, so at least I can rectify the problem the next time I apply. I'm a qualified Oral hygienist, wanted to venture in to Dental Therapy at this institution, I think my matric marks are fine , so I just wanted to know why? Was it my academics in varsity? was it my matric marks after all? Was it the fact that I already have a similar undergraduate degree? At least if I'm told , I won't attempt to reapply.