File exists, but getting 404

I created a new page: Demographics verify page You can get to it when you enter the url directly or if you click on a link on a page. But when I put it in a form as the action, I get Error 404. Like here: Form

To troubleshoot it, I’ve put other pages in for the form action and it works fine. But not this page. I’ve also tried renaming it, but it will not work as a form (even though any other page will).

Any ideas?