Registration Form Doesn't Submit

I’ve been beating my brain for the last hour trying to get your plugin to work on this site and it just refuses to do so. Registration fails every time. I’ve removed all non-essential plugins, leaving only the needed ones remaining (as in, plugins that I absolutely require for this site to function for the intended design). I’ve disabled caching systems, my CDN, all minification and compression stuff. It’s as bare bones now as I can allow it to be…. still won’t work.

Membership Pro 2 will not sign anybody up. You cannot submit your registration details, because the page will just refresh on you without sending the form. In the past I’ve had this issue, it was a caching problem. That can’t be the case this time, because I’ve already tested it all with everything disabled, including my CDN, and it’s still failing. I’ve also tried disabling everything I need active as well (but keep the same theme) and it still fails. I will not change themes for your plugin, especially on a live site, so that’s not something I’ve tested.

The server hosting the site is running Nginx.

I know this is my fault that I’m in a hurry… but I just started a contest, and people are trying to register and failing to do so. Take a look at this page. It has the contest, but more importantly, it has the links to register so you can see for yourself:

I’ve enabled support access on this domain already. Please help me. I’m feeling helpless right now. You have permission to do whatever you want to test this out and get it working. Thanks.