Every supplier (agency or tourist site) has the right to specify their own refund policy. If the product is marked as "non-refundable" it means you will not be granted a refund in case you cancel or miss your ticket/tour/activity time slot or departure time.
In the case of non-refundable products, a refund will be granted only if your reservation or the event is canceled by the supplier.
Please read the supplier instructions carefully. It is your responsibility to arrive at the meeting point on time and ensure you have all the required documents, are wearing appropriate clothing or gear.