Sims 3 launcher won't register new email

@swiftieforevermo  The only other way to restore the missing file is to uninstall and reinstall Sims 3.  But just in case this has a different trigger, you can try moving the Sims 3 user folder out of Documents > Electronic Arts and onto your desktop.  This would remove your saves and other user files, for the time being, but not delete them outright.

I saw this error a lot when 64-bit Sims 3 was first released, and it was always caused by either this missing file or by people trying to reuse downloads from a previous install.  If you've done that, please make sure you're downloading fresh copies of the content, in fact move the Downloads folder out of the Sims 3 user folder so you can be sure you're only installing the new files.  While this isn't exactly a new install, the new email may make it look like one relative to the files you previously downloaded.

The fundamental problem here is that Store content is encrypted, to prevent unauthorized sharing, but that encryption can also block people from using their own already-downloaded content on a new system.  It may also block you from using newly-downloaded content with a base game installed while you were still using your old email address; I have no idea.  But at worst, a fresh install of the game should clear everything up, and hopefully you don't even need to do that.