Envato has prepared a page about refund policy. Within that page, you will find :
When a refund does not need to be given (amongst other reasons) : they bought an item by mistake;they do not have sufficient expertise to use the item;they ask for goodwill
Of course if you really want to issue the refund, you can always override the recommendations set by Envato in that page. You have the ultimate decision-making power till they raise a dispute, following which I think Envato will use this page as a guide to resolving that dispute.
But you also need to check whether the buyer is located within the EU :
Additional obligations to EU buyers
If any of your buyers are located in the EU they may have additional rights over and above these baseline standards. We encourage you to seek any further information required directly from the website of the European Union Commission and consult with a professional advisor if necessary. As a guide, for those additional EU rights to apply, the buyer must be located in the EU and purchased your item for personal use only and not in connection with business, trade or commerce. If the buyer meets this profile, then we strongly recommend a mistaken purchase refund be provided for a period of up to 12 months from the date the customer receives your item, even if they have downloaded it.