Those that appear in your SG and Auctiva store front are seperate copies from those showing on eBay.
Did you enable Auctiva as the host in the listing editor ?
Have you accidently deleted them ?
It should be possible to examine the HTML in ebay -> revise item to see where the code expects the image to be. If this is all geek speak to you or the code looks ok best file an Auctiva support request with the ebay item numbers so they check it out for you.