Maintenance for the week of November 3:
• NA megaservers for maintenance – November 3, 4:00AM EST (9:00 UTC) - 12:00PM EST (17:00 UTC)
• EU megaservers for maintenance – November 3, 9:00 UTC (4:00AM EST) - 17:00 UTC (12:00PM EST)
• ESO Store and Account System for maintenance – November 3, 4:00AM EST (9:00 UTC) - 12:00PM EST (17:00 UTC)
• https://forums.elderscrollsonline.com/en/discussion/684716
You could be running into a connection issue preventing you from logging into ESO. If you continue to receive the message "Unable to connect to game server" when logging in you can go through the troubleshooting steps in the help article linked below.