This error happens also some month ago.
Which version of Safari and macOS are you trying to use?
I'm typing this reply from macOS 10.14.6 (Mojave) running Safari version 13.1.2 with no issues.
Catalina 10.15.6, Safari 13.1.2
Gotcha. I think you are using an alternate account. On your Mac, visit https://www.etcconnect.com/logout.aspx and then try signing in again.
Thank you, that was the problem.
