[Plugin: WooCommerce Print Invoices & Delivery Notes] Email Button Doesn't Work

When I click the Email Invoice button the order entry page reloads as if it did something, but it doesn’t send the email or take me to another dialog box. Is it possible when emailing an invoice to add a comment to it? I would like to be able to note Return Authorization Numbers in the body of the email or subject line when applicable.

http://wordpress.org/extend/plugins/woocommerce-delivery-notes/