The app was updated recently to version 1.1 - this is now available in all the app stores.
The update has removed the 'server selection' element so the user no longer has to set the correct server. This is now handled automatically via the PIN number that's entered for the game.
This solved the login issues some users have experienced. To date we've had over 3,000 players use the new app and not had the issue any more.
There were also some maintenance updates based on data that we've had recently.