FlyFF Private Server Help – "Cannot connect, please check your network" Error

Hi,
I’ve successfully compiled and launched all the server files for my FlyFF v15 private server (server .exe files + Neuz client). Everything starts up correctly, the .ini files are configured, the SQL databases are working, and the sources were compiled cleanly using Visual Studio.

However, when I try to log in through the client, I get this error message:
Cannot connect, please check your network

I’m looking for someone experienced with FlyFF private servers to help me:

Identify the root cause of this connection error,

Check that my AccountServer.ini, Certifier.ini, and other config files are properly set up (I’ll share them),

Make sure my IP address, ports, WorldServer settings, and network configs are correct,

Help me fix this final issue so I can fully connect and play.

Everything is currently set up on localhost (127.0.0.1).
I’ll provide screenshots, config files, and any logs needed — but no remote access.

Thanks in advance!