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.
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
dimified> @tkimnguyen Can you help me with my login on the community site?
rockfruit> I just met with someone who is also having issues loggin in there. Apparently, the "confirmation" email comes really late, and by which time it has expired.
dimified> wow
dimified> okay
dimified> haven’t received anything yet
@martior found out that the Discourse software upgrade, if re-run, fixes the problems we had been seeing. I confirmed that it had corrected a problem I had when I tried to get to a person's profile page to message them.