Whether fish breed or not has nothing to do with the shop you got them from, it will either be the fish themselves or the tank situation they are in now that affects their breeding. If you need to know more about keeping and breeding your fish, feel free to make another post in the relevent section for whichever species you are struggling to breed eg - livebearers, new world cichlids etc...
With so little information to go on and the risk of this thread turning out to flame the shop, I am going to lock it.