Hey there,

I am really sorry for the delay of this reply as it is a weekend for us here.

The reason why it appear these warning message after you logged in is because this "system - page cache" plugin already cached the login page HTML, mean when the user login failed then redirect to the same page, it will load back the previous cached HTML page so it will not populate that warning message.

I already help you disable that cache plugin, it should work correctly.

If you would like to use this plugin, what my suggestion is create a hidden menu for Easysocial login menu item from backend, then exclude this login menu item from the cache plugin setting.

Hope this will help.