Most problems with transactions can best be dealt with through the robots in the Resolution Centre at the bottom of this page.
If you are a buyer whose purchase is overdue, you can open an Item Not Received Dispute for 30 days after the last estimated delivery date.
If you are a buyer whose purchase is Not As Described you can open an INR dispute for 30 days after delivery.
If your seller refuses to refund you, open a Dispute and Escalate to a Claim.
If your seller persuaded you to close your dispute before receiving your refund, you are still covered by Paypal for 180 days from Payment.
If you are a seller whose buyer has not paid, you can open an Unpaid Item Dispute in the Resolution Centre at the bottom of this page after 48 hours from the purchase.