I've been trying to fix this myself for a couple of days but it is driving me crazy.
test site: http://test.ifanshare.com
In the header there is a login form. If you click the log in from facebook link the window pops up, enter facebook username and password and click the button... it begins the login process.
The page refreshes but you are not logged in.
It does however work from the wp-login.php page:
but also - if you go through the login process on the home page, then load wp-login.php and manually refresh it then it automatically logs you in without you doing anything.
So - it appears to me that when you login from the home page a cookie value is set on your machine from facebook. But that cookie value does not trigger the actual login until you go to wp-login.php, at which point it recognises that the session has started and writes and authenticated cookie.
I have followed the process through many php files, but can't yet find the hooks or functions I need to trigger on my homepage to make it all work...
I'm about to pull out my hair. surely it should be simpler than this.
Wordpress and buddypress are both latest versions, as is the facebook plugin.
All other plugins are up to date, deactivating all plugins makes no difference.
Has anyone else worked out how to get the login to work from anywhere other than wp-login?