Hello. Your question is incomplete, which makes it impossible for it to be answered. However, I was able to find a question like yours on the internet, where you were asked to solve this customer's problem. In that case, I hope the answer below can help you.
If the product was delivered on time, ideally, you should provide suggestions on how that customer can find the product, as well as give them a deadline for them to contact you again, if the suggestions have solved the problem.
Among these suggestions, you need to ask him to check if any people, who live in the same house as him, received the product. It is also important that this customer contacts the porters and the manager of the building where he lives, if he lives in a building, to find out if the product has not been delivered to someone else. Finally, the customer should ask the local post office if they have any information about this product. After these suggestions, it is important that you set a deadline for the customer to call you again if the product is not found. In that case, you must initiate the customer refund procedure.