as you all know if you are running your full site on https:// and serving images from https:// as well, it will cause an issue when listing on ebay. as ebay will not show the image when seraching for product or thumbnail.
for us the issue was, our images were hosted on differente server (STIC) for which we can not control of change any thing. as it will effect our rest of site. but the images are available on both https:// and http://, but we receive them as https:// becuase of ssl on our server
the issue is with ebay. They dont seem to like any image sent from https://
there is one solution for you. edit all products one by one and remove "s" from https://, but it is very time consuming.
we have contacted ebay and m2e pro, but both were unable to help.