Thank you for your help!
Here is what I tried without success:
- deleting the game and installing it again from the "new" copies on the EA app
- deleting the download folder
- clearing the cache of Edge & Chrome
- setting a new password without exclamation marks
- turning off my Norton firewall
This is what happens:
- The game itself with all packs seems to run fine.
- The previously installed store worlds couldn't be selected any more. Opening an old save in these worlds resulted in a black screen and a "severe loading error".
- If I try to download something from my store purchase history, the launcher opens and a "membership" login window pops up. This window never accepts my password.
- If I try to install store content from the old downloaded files on my computer, the process begins but fails at the end.
- It makes no difference if I install store content directly from the store or from the download dashboard within in game.
TBH the end of TS3 doesn't bother me too much, BUT I'm nevertheless scared that a hiccup of the EA app can destroy a 1000-€ game.
What if this happens to TS4? These technical problems are so difficult even to DESCRIBE, that there is no hope in the German customer service that barely speaks German.