Connect to Facebook issue

Hello. There is a problem in my forum on MyBB. I have installed a 'connect to facebook' plugin on the forum When I am registering, it is connecting with facebook, processing the same and coming back to the website for selection of username. Once I select and click on 'Register'. It gets stuck in an infinite loop. But when I close the page, go back to the forum and click on "connect to facebook again, I am logged in. I want to get this infinite loop problem fixed.