Response message not appear

Hello, I have a problem with the forms of the site http://www.hooms.it/, when the user clicks on “send” the message is correctly delivered to the email box, but no successful sending message appears on the website .

I have already used the plugin on other sites allocated on the same server and I never had this problem, I also tried to change the theme and disable all other plugins but the problem continues, I also tried to reinstall the contact form plugin7 but not it is solved.

What could be the problem?

Thanks a lot.

The page I need help with: [log in to see the link]