You are entitled to a refund or to a free resend in case of delivery failure.
Make sure to consult your uDroppy Supplier’s policies to know specific details about this case. Furthermore, remember that “delivery failure” refers to the product still being in transit or declared lost at the moment of your request.
In case of failed delivery attempt, which means that the causes depend from your final customer (i.e. not home, wrong or incomplete address), you are not entitled to ask for a re-send rather than a refund.