A bid or purchase on eBay is considered a contract and you’re obligated to purchase the item. However, if you feel that you have a legitimate reason for not buying the item, you can contact the seller and explain your situation. Many sellers are willing to work with you if you communicate with them openly and honestly. If you haven’t done so already, request the seller’s contact information and call him or her. Possibly, things can be worked out to everyone’s satisfaction.
If the seller doesn’t respond in the way you hope, keep in mind that failing to purchase an item you have won can result in an unpaid item strike being filed against you by the seller. If you get too many strikes in too short a time period, your account may be restricted or suspended.