My freezer works, but refrigerator won't cool

[dragon600]

I recently purchased a mini fridge and everything worked fine. After a couple of months it stopped cooling in the refrigerator, but the freezer is ice cold. I unplugged for a couple of days to see if it needed defrosting, but after plugging back in its the same issue. I’ve moved the cooling dial around, and it seems to make no difference in the fridge temperature. I cant see where there is any vent from the freezer to the refrigerator like a full size refrigerator. Is this a common problem with this unit? Thanks