You are also covered by your Paypal account for 180 days from payment and by the credit card you attached to your PP account.
But you can open an Item Not Received within 24 hours of the delivery date, if it has not arrived. Although you have up to 30 more days.
The seller then has to prove delivery. No delivery, you are refunded.
For a Not As Described the item has to have been delivered (duh!) but again you have 30 days from that delivery date-- even if it were "late".
Is it eBay telling you a "Returnable" deadline or is it the seller?