Checkbox not working in Boxzilla pop-up

For some reason users aren’t able to subscribe to my mailchimp newsletter because the checkbox isn’t clickable in the pop-up. Is there a way so that this doesn’t happen?

I was trying to find an answer for this and tried this code:

#mc4wp-form-3 input[type=”radio”],
#mc4wp-form-3 input[type=”checkbox”] {
display: block;
}

However, it made two checkboxes. But when I clicked one checkbox (the ugly non CSS checkbox) it clicked the normal checkbox…

In the pop-up I am linking to the shortcode.

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