Laravel 5 auth - register redirects to itself

My laravel 5 application uses the official auth framework. In my homestead/vagrant environment, all works well but when I try and deploy to the production server, the auth functionality doesn't work - for example, if I try and register a new user, the form redirects to itself and doesn't create the entry in the users table.

Homestead vagrant is running nginx, and the production server is running Apache 2.4.6 (something I don't have control over). mod_rewrite is enabled and the public/.htaccess is as below:

Options +FollowSymLinks
RewriteEngine On

RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]

I've checked the laravel and apache logs and no errors are logged.

The Apache virtual host configuration is

<VirtualHost *:80>
  ServerName example.com

  ## Vhost docroot
  DocumentRoot "/var/www/app/public"


  <Directory />
    Options FollowSymLinks
    AllowOverride All
  </Directory>

  ## Logging
  ErrorLog "/var/log/httpd/laravel_error.log"
  ServerSignature Off
  CustomLog "/var/log/httpd/laravel_access.log" combined 
</VirtualHost>

via Chebli Mohamed