Sims 3 Version 1.0.631.00001 won't update on my Mac

I bought the Sims 3 years ago when it first came out, and I just decided today to install it on my new computer, a Macbook. I was able to install it, but my version is outdated and I want to install custom content, so I keep trying to update it.

When I run The Sims 3, the Game Launcher repeatedly tells me that there are updates available, but when I try to download them, it stops after a few minutes with a message that "There are no patches available for download." I've tried to manually install them too, but I'm not sure if that works for Macs, and it hasn't worked for me.

So now my Sims game is stuck on Version 1.0.631.00001, and I don't know how to update it so I can install custom content. What do I do?