On English Language & Usage SE and now on main on this SE: I am asked to log in, refused entry because I'm not in the database, and then ... on meta, it knows who I am.
And here I am. Asking this same question. I'll link back to this question from the ELU meta Q.
Currently, we piggy-back on the main site's authentication cookie to initially create your meta cookie. This is why clicking "log in" on a meta site will redirect you to the main site's Log In page.
However, if the main site's cookie is somehow removed, you can still be logged into the meta.
If this happens, just log in again on the main site.
We're going to change how this works to help avoid this duality: if you're logged out of the main site, you'll also be logged out of the meta. This change will go in next week.
In order to see if it's really a bug, try making a hard refresh of the site. Delete the cache, and reload the Main site. It should re-ask you for your login, but if you wait 3-5 seconds, it will automatically log you in again, I think.
And by then it should be fixed. Let me know if this works.
