May 2019
I have bought, installed, and even played the Sims 3 Pets on my computer. However, I stopped playing Sims altogether for a while due to personal issues. When I got back on the game, the Pets game had disappeared. When I look the game up in Origin, it says I have purchased it. However, it does not show up in my game library or gives me the option to download it again. I don't think its a problem with my computer because I have since bought the CD version of Sims 3 Supernatural, and I have had no trouble with it whatsoever. I bought the Sims 3 Pets through Origin.
May 2019
@FireintheNight1 In your Origin library, if you click on More > Expansion Packs and scroll to where Pets is listed, what does the button say? (Play/Download/Details/Buy Now) If you're seeing a prompt to buy, try clearing Origin's cache. If that doesn't work, uninstall Origin "the hard way" and then reinstall.
https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/
https://help.ea.com/en-us/help/origin/origin/manually-uninstalling-origin/
If these steps don't help, you'll need to contact EA customer support. Since you can see Pets in your purchase history, a support rep will too, and can try to help you fix the issue. Sometimes packs get blocked by mistake, and it takes an intervention by a support rep to fix it.
https://help.ea.com/en/contact-us/
May 2019
I think I have got it working now. It's showing up in the launch thing and is working while I am playing the game. I sometimes have to open and then close the launcher for it to appear, but otherwise, it seems to be working fine now. Thank you though.