When you launch a game via Steam, whatever login details you originally provided will be used to start the game and automatically log you in.  If this information is incorrect or no longer accurate, you may experience problems.  

Unfortunately, Steam has saved the incorrect data to your SteamID and we have no access to this. Simply deleting the game yourself will not reset the data which Steam has stored, only Steam Support will be able to remove the game from your Steam Library.

As a first step, open a ticket with Steam Support and tell them the following:  the game's data is corrupted and will not launch correctly, and ask them to remove the game from your Steam library. After they remove the game from your Steam Library, be sure you have also installed the game from your computer and you should be able to download the game and enter the correct or updated login details.