Steam users didn't notice problems with logging in game with the new launcher released yesterday.
I just want to explain how steam users can use the manage-account interface on the website again.
1- you need sadly to download the new Gameforge Client from the website and create a new account (it's ok if you use the same email of before)
2- install the Gameforge Client granting administrator permissions
3- open the Gameforge Client with your new GF account
4- select Tera from the available games
5- click on the icon with the little man + and choose "add an account" then insert your old email and password - now you should have linked your account tera to the new client
6- click on the nickname that will appear near the same icon and choose "settings" : it will redirect you to the old page on website where you can manage your account (shop, char transfer, TC etc) - no need to download the game if you still want to use Tera through Steam