In order to ensure that 2Checkout calls back your Kartris site to notify it that a payment for a particular order was made so that confirmation mails can be sent and the order can be tagged as 'paid', you need to set up a few things within your 2Checkout account.
2Checkout should now be set up and working. We would advise that you always test a site in live mode when you first open it (status = 'ON') even if all the test modes checked out ok. This confirms that everything is working with Kartris and that your account with 2Checkout is live and working. The best way is to create a low value product of a dollar which you can purchase.
Ensure your page has the following code pasted near the bottom, before the closing 'body' tag.
Copy this code and place it where you want the help icon to appear in your page.
Your help link will appear as the icon below. Click it to verify how the help content will look.
Place a QR code on your product or machinery to let a user easily retrieve the user guide documentation for it.
Right-click and 'copy'