If the purchase is made through the 2Checkout (Verifone), you can download the PDF version of the invoice. In order to do that, log in to your 2Checkout account with your order number or email.
Access the My Products - Order history section. Then please click 'Download invoice'. 
You will be able to preview and download the invoice as PDF.
If any questions regarding the invoice arrival or information, please contact 2Checkout Support.
If the purchase was made with Stripe, or other payment system, please, contact us via our Support page to request the invoice.