Thank you for your suggestions, I did go through those when I first started troubleshooting.

I’ve already completed all of the common fixes you listed:
- "DirectPlay" is enabled
- Required ports are open
- Firewall was disabled for testing and exceptions were added for both PlayOnline Viewer and Final Fantasy XI
- Antivirus was fully uninstalled
- Router/network has been tested, including an alternate connection (mobile hotspot)
- Clean reinstall and testing on a new Windows user profile

The issue specifically occurs at the moment I click “Accept” on the EULA and the error appears. At this point it seems less like a basic connectivity issue and more like a session/handshake failure during the login transition.

If anyone has encountered this exact behavior on Windows 11 and found a solution, I’d really appreciate hearing what worked.