Cross-promotion of products on our thank-you pages is temporarily disabled, as noted on the help page for that feature:
If your product is a subscription to an email series, rather than a file download, you would not use the Single File Download setting for that product.
After the buyer finishes checkout and the payment processor confirms the buyer's payment was good and completed, we grant the buyer access to a unique thank-you page we generate for each transaction. This page is where we would automatically present the buyer's unique download link(s) (if they had purchased any) along with any thank-you page customization you had added in your account/product settings. Depending on which payment processor was used for checkout, the buyer may need to click a link on the payment processor's checkout site after they finish checkout in order to proceed to a thank-you page.
@whispers: you would only need to enable "Send Transaction Data to a URL" if you wanted us to forward the order details to a custom/3rd-party script for additional processing after we're done processing the order for you. That setting is not necessary if you're just using E-junkie to sell and issue download links.