Hello,
i figured out that your royal theme has problems in the checkout if i use a plugin for generating invoices. I want to use https://wordpress.org/plugins/woocommerce-pdf-invoices-packing-slips/ but if i activate the plugin with your theme i get the following:
When I have filled out the form at checkout and then click the order-button, the site dimms a little bit to white and and nothing happens. Normally then there will be the order confirmation page.
Looking for it in firebug shows an error with “…admin-ajax.php?action=woocommerce-checkout”. This throws an 500 Internal Server Error.
But the email with the pdf attachement is sent correctly.
Hope you can help!!!