I've had this issue for the last couple weeks. I'm getting the following error in a dialog box on my Playstation 5:

"Can't Connect to the Server. There might have been a problem connecting to the network, or Playstation Network or the server of the service provider might be temporarily busy" with an error code of WV-109144-9

Behind the dialog box instead of the login screen is a blank white page with the following text

ERROR: 0x00000006
SSLError: 0x00000000
Couldn't Resolve Host Name

I have determined that it it just FFXIV with the issue as I have tried online multiplayer with other games and those work (Overwatch 2, Call of Duty, Battlefield) . I get the same error with the PS4 and PS4 versions of FFXIV.

I've tried the following
Wired connection with default settings.
Wired Connection with manual DNS
Wired Connection with PS5 assigned to the DMZ

The game does work with wireless enabled, but I get slower upload and download speeds with that. Ideally I'd like to keep the wired connection to the internet for when I download new games.

I like to remote into my PS5 sometimes to play while I am away from home via my iPad plus Controller.

Router is updated with the latest firmware. PS5 is up to date as well. BOth games are updated to the latest versions.