When you installed your Sims 3: Pets (or other expansion), is your whole game crashing and won't let you play?
Here are some things to try.
1) Please uninstall Sims 3: Pets by dragging the icon from your Applications folder to the trash
2) Go to Documents/Electronic Arts/The Sims 3 and delete this folder. If you wish to keep any save files, please back this folder up by saving it to a USB or dragging it to your desktop.
3) Go to /Library/Preferences/The Sims 3 and delete this folder if it appears here
4) Launch your latest expansion pack/The Sims 3 game by clicking on the icon in your Applications folder
5) If there are any updates that prompt you automatically, please download them
6) You should see the game’s launcher. On the left side please select “Game Updates” and then press “refresh”. Please make sure the “Automatic Updates” is checked and that it says your game is up to date.
7) On the top left hand corner of your Mac desktop, please click on the Apple logo and select Software update. Please install all updates.
8) Go to your /Downloads folder and find your .DMG file for The Sims 3: Pets to start installation process. Sign in with your EA/Origin account when prompted and input your serial code that is inside your download e-mail from us.
9) When complete please launch the game and install any new updates if any.
10. With the launcher up, on the bottom left hand side you will see a version number. Please take note of this version number if you are contacting support
11. Please note that on the bottom of your launcher you will see a row of The Sims 3 expansions and stuff packs. The highlighted ones are the ones that have successfully installed.