When I go to log into Gmail I get “Unknown Error”

Firefox 58, OpenBSD. I know old software is bad, yada yada, but can we not break stuff like log in prompts? I have wasted over an hour today trying to log into my email. I enter the user name, then click next, and then the web page returns "Unknown Error" from google. What the hell? Yet another reason not to use google products. In about 20 years of using web mail services I have never been prevented from logging in by an "unknown error."