We have since pushed an update that should fix the majority of toons for everyone, but you may still notice that some of your characters can't be logged into, or that you just get stuck at the loading screen.
If this still happens to you on the current testcenter, please post the following:- Toon name(s)
- Username you use to login for each toon
After doing so, I should be able to reattach them to your accounts.
Sorry for the trouble!