@5b66fbdad684fe70 You'll need to use the same email address and password you do on other EA sites, and the password cannot have certain special characters in it. If necessary, change the password on ea.com. And delete the file labeled [your email].bin inside Documents > Electronic Arts > The Sims 3 as well.
Having said that, there's no reason to login to the launcher, at least for most players. The Main Menu's login option only adds a few features that are mostly trivial: Simport, gifting friends, earning badges. So you can play without either login and not really miss anything.
