Rest assured, we are doing our best to come up with a workaround to try to resolve this issue. It's an ebay bug, where ebay is not supporting secured images. We already have a case open with ebay and they are working to resolve the issue. You can replicate this problem on the ebay site, when attempting to upload a secured image (an image where the url starts with "https") using the "Import from web" link. The same ebay bugs impacts users of the ebay API, applications like Auctiva.
With that said we are developing a workaround to resolve this issue until ebay can get the bug fixed. As soon as we have the fix in place, we will let the community know.
Thanks for your patience,