You have to negotiate with the seller to solve it before this time and decide whether to resend it. When the timeout is approaching, you should initiate a refund application and save the payment first. These exchanges are completely acceptable to the seller.
It may be reasonable for your seller to keep you waiting. He doesn't ask you to wait for a solution between him and the courier, or deliberately delay your time. He may ask the courier company to find the goods and make sure that the goods are lost and cannot be recovered.
If the seller does not recommend resending, you can initiate a refund application at the appointed time.