This error has plagued me for years, when you login to the website via the buddypress widget on the right, or via the direct wp-login.php even if its successful, the page you are on when you logged in is not updated to show you logged in successfully, sometimes if you visit another page it'll show you as logged in, sometimes you have to login a good 3-10 times for it to actually show you are logged in! Is this a cache issue? Theme or plugin issue? I use Buddypress, BBPress, Totalcache and were pushing through cloudflare. I have a lot of security plugin that could also be conflicting: Akismet, Bad Behavior, WangGuard, Wordfence Security.
This community seems to be mostly development but the description says administrators are welcome, and my post has been ignored on the wordpress forums for 4 months now.