No action on form pages after hitting the Send button.

My form pages were working perfectly for the past 3 years, then over 2 weeks ago they just stopped working, I just get the twirling arrows like they are doing something, but nothing happens. And it’s not just me, I only knew about this because many people emailed me to ask me why my registration page and other submission pages are no longer working, that the twirling arrows just keep twirling instead of the form page getting submitted and them receiving a link to continue to the next page. I restored my website’s WordPress folders and files to 3 weeks ago, when they were working, but it’s still not fixed. I was using WP version 4.1.1 so I updated to 4.4.2 to see it that would fix it, but it didn’t. Any possible solutions out there would be highly appreciated! Thanks! Here are some of my form pages that are no longer working:
https://romancenovelconvention.com/registration/
https://romancenovelconvention.com/schedule/class-submission/
https://romancenovelconvention.com/attending/i-am-attending/