cats and dogs add on won't work

So, before I don't really know when, a few months ago though it stopped working, and before that I could use it, now It just doesn't work, like it says I have it but It doesn't show anything/I can't make pets, I don't have anything from it now, and I'm playing on my Mac. which works, but I don't understand what to do to like fix this problem and I haven't played in a while because I can't use the add on of cats and dogs. which I really love to use/play with, but now I cannot do anything with it, which I am sad about.