I never activated TFA, but it's activated

I received a notification from gitlab.com that my account has been locked because of excessive login attempts. These attempts were not by me. I clicked the link to unlock my account and attempted to login with my gitlab password and my github and google accounts. In each case I was presented with the 2FA code verification screen. I have never activated 2FA at gitlab.com. I do have Google Authenticator installed and use it elsewhere, but I’ve never used it here. (I also can’t find a support email address anywhere. Do we really have to use the community forums for this sort of thing?)

How do I go about resolving this situation?