Comments not submitting

Hi there,
I just installed this amazing plugin, but it isn’t working for me… I’m using it with the Vemilion theme (Rockettheme / Gantry), and when I add a comment to the guestbook it keeps saying “Submitting comment”…

Anyone who has a solution?

Kind regards,
Rick

https://ww.wp.xz.cn/plugins/comment-guestbook/