Forms & Widget Not Working

I have been having success with sending newsletters, but when I go to Settings > Forms and try to create a form to leave in a page, it simply does not work. In posts, the envelope icon is present, but an empty popup box shows up and nothing else.

The same thing goes with the widget – I have the widget bar, and when I install it in the footer of my homepage, the form shows up. But when I press “subscribe” nothing happens.

Is anyone else having this problem? Any help is appreciate. It’s a great plugin except for these two crucial elements.

Thanks.

https://wordpress.org/plugins/wysija-newsletters/