I am pretty certain that eBay's rules are based on claiming before so many days after the "estimated delivery date" stated by the seller, else you lose the eBay guarantee - the PayPal guarantee is valid much longer. Some sellers are slow and a few seem distinctly reluctant. Recently eBay told me I should not give in to requests for waiting a bit longer once I was aware of a failed delivery. I usually advise the seller within a day or three that the item has not arrived. If I have no response from the seller of a failed delivery then I send a message saying that if I do not hear (usually within 48 hours or so) then I will activate the eBay failed delivery refund procedure. This gives the seller 7 days to respond. Recently I had such a response which was aimed at delaying the decision further, I refused and got the refund. In more than 600 transactions (purchases) in more than 25 years I have had perhaps 10-15 failed deliveries and got refunds on them all (if I am not mistaken).