both lemmy.ml and lemmy.world have had login issues for the last 2 days-- and 2FA isn't the issue.
from what little I've gathered from various posts and the lemmy matrix chat, both sites were experiencing a massive DDoS attack, and may have disabled logins, however, that doesn't explain the lack of communication from either team or how long it's been disabled (almost 2 days).
current session still work, and (at least yesterday) resetting your password was a workaround to log into you account, but if you log out, you can't log back in again.
this is all I know so far...