In IRC rei0004d reported being unable to log in with his github account "dimified" nor with an email address. He tried with Chrome and Firefox. I saw several of these errors in the Discourse log: https://community.plone.org/logs/show/87bdc3e8aa15eba61f38e4afca827b60 as a result of his login attempts.
I was able to log out of Discourse then back in again with my Github account without any problem.
(I myself also ran into the last 2 days or so a problem "liking" a post, for which there are 33 of these errors https://community.plone.org/logs/show/2371bc6c9e5af6208500cf1c01a3a30c )
Has there been a Discourse upgrade recently?
06:23 Something went wrong, perhaps this email is already registered, try the forgot password link
06:24 with github and create new account
06:24 also something with cookies