There isn't supposed to be a pre-configured user. The account_data table should be empty. Here is a screenshot of my network.properties for the login server:
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Manually creating accounts using SQL might be buggy, as Aion hashes the password and unless you know HOW it hashes the password, it might not read the password correctly. Which might be the problem you're having. You're entering a password for an account in plain text and the game thinks it's a hash and tries to decode it.
With
loginserver.accounts.autocreate set to "true", you're supposed to be able to enter any username and password, and the game will check the DB and if the account name doesn't exist, it creates an entry for it using the name and password you used.
Edit: One thing I would suggest (This is my problem with my Aion server) check to see if, in your login folder, you have a "build" folder. If you don't, disregard the next part of my post.
If you do, open it to see if you have a "dist" folder in there, then open the "dist" folder to see if you have a copy of your login server folder in there. In my Aion server, for some reason unbeknown to myself or even the gods, I have two separate configs for everything. Any modifications to game files I want to make, I have to make them twice: One in the normal location, and one nested in the "build\dist" folder If you have this duplicated folder, make sure you make the settings changes inside there as well.