I'm experiencing the same problem.
Last evening it worked just fine, I even ran a Windows 11 update right before I logged into FF14. Played for a bit and logged off just fine, no warning, no issues back then.
Now I want to log back in on my laptop and I get the same notification as you all do.
Funny thing is, I could log into my account on my sister PCs. We go online via the same router so I doubt it has something to do with the internet connection when I can log in on her PC without any problems.