So, the method of google login for the forum was the same deprecated method the game was using a few months ago.
I have disabled them for the forum as well, but would love to help making sure google folks can create a password and login without the google login button.
If you previously logged into this forum using google, please try logging out and see if you can get back into your forum account by resetting your password.
If you fail and need help, you can email me on firstname.lastname@example.org
edit: I did it myself last night, but would love others to test as well.