If you do not pay by a certain time he can open a case against you as a non paying buyer to get his fees back. If this happens it goes as a mark against you. You can accept his cancellation offer with no mark against you or you can force his hand buy paying for the bike. What did the notice say?

Edit. He opened the case against you. I just noticed what you wrote. You will have a mark against you if you do not buy the bike. To many of them and you can get kicked off ebay.