When i click on the 'Send' button, the page redirects to the standard language of the website, see http://www.belmoca.com/en/register-machine/. When you click on 'Send' it goes back to http://www.belmoca.com/register-machine/.
Just curious here, but can you try something for me - can you remove the reCAPTCHA field and then enable AJAX on your form shortcode placement to see if that helps?
Thanks Rob! That was the problem!
Right on, glad to help!