@devin :
the reason why it does not work is that the plugin requires PHP sessions to work. WPEngine disables PHP sessions for non logged in users for caching and server optimisation purposes. In fact, PHP sessions are stored on the server and WPEngine is all about resources optimisations and performance.
@miled :
more and more people are going to use WordPress-only hosts in the future and even some homebrew setups might have php sessions disabled to improve server performance.
Other social connect plugins do not use php sessions to work. Would it be really difficult to find a workaround for your otherwise excellent plugin? like using cookies only?
cheers