Can't Submit Form

Hey. We use this great plugin on our site. Recently we’ve had a problem where the form won’t submit for some of our users. The user inputs their email address and fills out the required fields and then clicks submit. A little spinner shows up next to the submit button and then goes away. The from is still there but clicking the submit button again doesn’t the same thing. When it’s working properly the form disappears and a Success! message shows up saying we’ll email them shortly.

The confusing part is that this doesn’t happen to every user. Even more confusing, if I edit the wordpress page, remove the form, and then put the form back it seems to work fine for the rest of that day. Some time after midnight it seems to break for certain users again and our support inbox will have emails from users saying they tried to fill out the form, but nothing happened when they clicked submit. Any ideas?

https://ww.wp.xz.cn/plugins/mailchimp-for-wp/