Refusal to authorize chronic medication

Yesterday I went to get my “ chronic “ medication from Clicks and I was surprised to be told that the Medical Aid was not authorising the meds because “ the funds are exhausted “. I’m confused now as to what my MSA have to do with Chronic medication ? I had to pay cash for the tablets because I need them. I couldn’t pay for the other expensive ones as I don’t have money and I wasn’t expecting to pay for chronic medication. Can someone please explain the reason for the refusal to authorize.