I got Sims 4 when it was free in May and when I got a new computer I can't see it in origin. I am on the right account, it doesn't even show in the order history.
@cupcakesinthemor I've moved your post to the Origin tech section, since this is an issue with Origin or your account, not Sims 4.
Please make sure you don't have any filters enabled in your Origin library. The filter icon is in the upper right corner of the window, and when you click on it, you should see the option to dismiss all filters.
Is Origin loading properly, as in, are you online and can you see the store content? What happens if you look up the Sims 4 base game—does it ask you to repurchase? Does your new computer run Windows or macOS? You can force Origin to refresh its data by clearing its cache (Windows) or running the Origin reset tool (macOS).
If none of this helps, you'll need to get in contact with EA customer support so that someone can check your account. You should definitely still have access to the base game, but glitches in the system do happen.