@Theta-3119 Is it possible that you have an antivirus/firewall blocking the store from loading properly? You can try disabling it temporarily, just long enough to test. The store itself is up and running—I just clicked around myself, and I could load all the world pages I tried, as well as the page to register codes. So it may be something with your system, your account, or your connection.
It would also be helpful to know whether you can login to the official Sims forums. That site uses the same login as the store, as of the recent store maintenance last week. If you can't get into the official forums, the problem is likely the login function. If you can, then there's something about the store itself that's conflicting. Also, if you're logged into the official forums in your current browser, you'll automatically be logged into the store when you visit, so that may be a viable workaround.
If none of this helps, please list your OS and the browsers you've tried. I can ask an EA community manager to look into this, but it will need to wait until tomorrow.