I am currently having issues with FFXIV, no matter what nodes I connect to, I am constantly getting error messages where I disconnect and then reconnect a bit later. It happens regardless of whether my own internet at home is acting up.
I have tried with FastConnect on and off, I have it set to TCP, I have tried with both auto-selection and manual selection for nodes and nothing seems to have helped.
Please confirm that How to check the basic functionality works fine in your environment. It’s a first thing you should test.