Decline Page
The flowchart on the left describes 2 different cases when payment gets declined.
Payment is made for the main product
Customer is redirected to Decline page with CTA button labelled as Go Back.
Clicking on Go Back button takes customer back to the Order page to place order again.
Main product is paid successfully, payment for upsell is declined
Customer is redirected straight to Confirmation page, showing the Order details with paid items.
No Decline page is shown as confirmed with @Pascal Rossol (Unlicensed).