Been trying to log in for past half hour and can't, ever since I patched doesn't seem to ever go past the login screen. Yet it sais servers are up, this stuff should not be happening.
I was receiving the same error this morning.
1. Close ESO window & Launcher
2. Right click the launcher Icon on desktop
3. Click run as "Administrator
4. Launcher > Play = This got my ESO working straight away. (hopefully works for you!).
No the firewall is fine, game worked fine yesterday and the day before and the day before that etc etc etc..... My modem doesn't block it, and my firewall doesn't block it. It stopped connecting right after it patched.