Good afternoon and thank you for posting on the Final Fantasy XIV Technical Support Forums.

If you can log into the North American Data Center but not the European Data Center, it would suggest some sort of connection issue with the EU server. It's possible you may be physically closer to the NA server, but I don't have your rough location. It's more likely you are being routed through a troublesome area, however, without a trace route I can't tell for certain.

In case it is not a connection issue, I would suggest doing a clean boot, by simply opening up the task manager and clicking the start up tab. Disable everything here and restart the PC. Also make sure that any anti-virus or firewall you have has an exception for Final Fantasy XIV.

We hope we can be of assistance in helping you enjoy the exciting world of Final Fantasy XIV!