Just wondering how can I send an invoice to the customer as shown in the attached picture.
This seller sending the order confirmation email with a link to download the invoice. When you click the Download Invoice link it just download a copy of the invoice.
I apologize but I am not quite sure I understand the question. Selecting the ‘Download Invoice’ button’s intended purpose is to download the invoice. Are you looking to send the customer a new invoice? Or resend the order confirmation email?