Title says it all.... here is a gif of what my problem is..
what is your forum url & which theme you are using as the default theme (main theme) ?
Well, your forum isn't sending the my_post_key with the AJAX request to verify the username. The source code looks good, it's equal to the one of mybb.com. But I am getting console errors for your javascript files, could you please re-upload them (they're in the folder jscripts)?