Heya kayleighmaia4
If this started for you after an account merge, it sounds like we'll need the live support team to manually regrant your Sims 3 content to your account so you can access it again.
This isn't something we can do for you over the forums as we don't have access to your account details, but live support can be sure you have the correct current versions added. Please reach out to live support from the site here for more help on this- I'd also recommend attaching this forum conversation when you reach out so the team has additional info to reference.