Sims 3 wants me to register my game with a serial code I never got?
@Despop919 You don't need to login, either at the launcher or Main Menu, to play TS3, whether in your new store world or any other. The way you get that world into your game is by downloading it into your game folder through the Sims 3 store. Go to the store, login, click Store>My Account>Purchase History, and you should see every store item you own. Click Download, then wait a few seconds for your launcher to open. (You don't have to login at the launcher for this to work.) Once the world is downloaded, check the box next to it and hit install. Make sure you're only installing the world and nothing else, as the launcher can't properly install a lot of data at once.
When you've installed the world, it will show up at the Main Menu, as part of a dropdown menu, when you press the button that says "New Game." Again, you don't have to be logged in for this to work; the store world will load and play like any others you have installed.
If you want to login while playing, I'll repeat my advice from before: Clear all of your browser caches, including the one for Internet Explorer, and make sure to uncheck the box to preserve data for favorites. Then change your password at the store site. Then clear all of your browser caches again. Then launch the game and try to login at the Main Menu, not the launcher.
If you can't download and install the world, that's a different issue, but it's certainly solveable. If you can't find that world in your purchase history, and the code has already been used, then you'll need to contact EA customer support for assistance. No one here can fix that kind of account problem.
