Thank you for posting in the Final Fantasy XI Technical Support Forums.

We’re glad to read that you are able to log into the game, it does seem like it is a Windows 11 issue since the latest update has heightened security. For now we suggest staying on Windows 10 as a temporary solution. Please do not hesitate to contact us if you encounter any other issues, we do again apologize for any inconvenience you may be experiencing.

Thank you for posting in the Final Fantasy XI Technical Support Forums!