Hi,
I have got the same issue with changing the world as many in this forum.
I got a tip from other player today what seems to work for my 2 accounts in this game.
So do not try to change the world in start screen after you have logged in.
You need to log in and enter the world where you go in.
Then go to the options in right down corner and there, my games.
Change the world from there.
So in this morning, after doing this, I was able to log in my other worlds after 3 weeks of waiting....
I also got other tip that sometime it helps if you change the language but I haven't try this.
So guys, try this if this works for you....
-Late-