Says code is not valid and won't download...

first seek a refund on the second purcahse as you already own it second the code  should be redeemed in your the sims 3 account not origin  if you did redeem the code in origin that can make the code invalid/used if that happened you need to contact CS for that too

also worlds are sims 3 store DLC items once you have the world downloaded and installed it will be in the main menu +new game to select the world to play in you will still play from whatever game you normally play from also there will be no launcher icon shortcut desktop icon nor will it be in your origin my games tab

if in the event you need to contact CS

1.https://help.ea.com/en/contact-us/
2.Click on the orange NEXT button
3.Select a platform
4.Click on the orange NEXT button
5.Select a topic and describe your problem in a few words
6.Click on the orange NEXT button
7.Click Chat Now to chat with a Game Advisor


guide on how to contact CS

http://answers.ea.com/t5/Beta-Archive/How-to-contact-a-Game-Advisor-using-the-new-EA-Help-page/td-p/2161281

to redeem the code

1. Go to thesims3.com and log in with your account
2. Go to the general redeem a code page: http://www.thesims3.com/incentive/generalredeem.html
3. Enter the 16-letter code (this is not for 20-letter codes) and click on Submit
4. Go to your purchase history to download the world (make sure your game is updated to the newest version)