The right of cancellation expires for a contract about the dispatch of digital downloads by using download-links and not by physical-Data-media if the customer has given his agreement explicitly that after the order is completed the customer has no right of cancellation anymore.
This is because of the fact it can not be proven in case of cancellation that the customer has not saved a copy of the concerned digital files. By hitting the “Buy”-Button on the Checkout Page he agrees with Cancellation Terms.