My site is currently just displaying a generic "404 - not found" page when users hit nonexistent pages. I tried editing the theme's 404 page but nothing changed, then I tried adding a 404.php file to my Public directory but no luck, and I also tried adding a 404 plugin to the site but it's still serving the same message. I'm on a shared server so I can't access the .htaccess file.

Pretty new to WP, where can I find the 404 page setting to have the site use the default theme 404?