I have an eBay listing with a slightly customised Pro store GarageSale design. My store logo and footer logo are hosted on Google’s https servers. My logos appear when looking at the listing on an iPhone but a little blue box with question mark appear when looking online on a browser…
This might have to do with the sandboxed iFrame eBay puts the item description in, I am not sure.
Maybe it just has to do with the empty spaces you’re using in your image’s title. It’s worth a try to remove them, re-upload the image and insert the new URL in your listing.