If you get this error while starting a game you have most probably downloaded the start file, saved it locally and are trying to execute it.

That will only work once.

The working way to start the game is:
  • Log in to supremacy1914.com
  • In your "User Menu" click on "My Games"
  • Click the play button of the corresponding game.

It is advised, that you do not download the file but instead launch it directly by selecting "Open with Java Webstart" and marking the check box "always choose this action for this filetype".

Why this?
The downloaded file contains a login password for the round you're trying to get in. If it wouldn't contain such a password we would have to ask you every time you open the game. For security reasons, the password will only work once (Otherwise everyone who gets access to that file could use it permanently to log in to your games). So if you try to use the same downloaded file twice for logging in to the round, it will not work.

Have fun playing!