@SapphireSharon Try clearing Edge's Internet Explorer-mode data:
https://support.microsoft.com/en-us/microsoft-edge/view-and-delete-browser-history-in-microsoft-edge-00cf7943-a9e1-975a-a33d-ac10ce454ca4
and deleting the file labeled [your email].bin inside Documents > Electronic Arts > The Sims 3 > Downloads. These are where login data gets stored, and it's always good to clear both if any details change.
If that doesn't help, would it be possible to go back to your old email address? If not, maybe there's a workaround, but it might be easier to just use the old address.
@meradol Are you currently seeing issues with the Store site? It's been down here and there for a couple months, but it does work most of the time.