I'm from Australia also and also having the same problem.
This is the second time it has happened (the first time was only just a few weeks ago with patch 5.1!)
I have tried these solutions and none of them have worked for me :
-Tethering to phone
-Changing to multiple different DNS's (1.1.1.1, 8.8.8.8, 4.2.2.2)
-Running as Administrator
-Disabling Firewall
-Uninstalling and Re-installing the game
-Changing to the old launcher
-Multiple VPNs (NoPing, Mudfish with Full VPN AND Cyberghost which worked the first time for Patch 5.1 but I'm not eligible for another 1 day trial and I refuse to pay just to download a patch)
I've been playing FFXIV since ARR and this problem has only just started occurring since Patch 5.1 and I would hate it for it to happen every patch.

I hope with enough exposure that this problem can be acknowledged by SE and fixed as soon as possible!!