Solved
New User Account Loop
I bought Sims 3 digitally and I log in using my origin details. It automatically takes me to a Sims New User registration page and I fill in my details. It tells me the persona is available and I check the terms and conditions box. then press sign up and the page essentially reloads. This is all done in game.
Try another browser and make sure you have cookies enabled.
If you're trying through the launcher, use the website instead.
