We have received a number of reports of this nature in the recent past and, in each case, we have found that the items in question were not configured to use Auctiva Checkout. Ebay went through a technical issue that was causing the third party checkout system to be dropped during the relisting process, so I'm inclined to believe most of these reports were a result of that issue.
In any event, please feel free to contact our customer support department regarding this issue using the appropriate link on our help page, http://www.auctiva.com/free-auction-software-help/help.aspx, and we'll be happy to look into your specific case.