I'm just trying to add media to my product using this URL: https://greenchoice.gumlet.io/sm-gc/00028000823177.jpg but Shopify refuses to use and gives that error. Looking at the file metadata:
$ identify -verbose 00028000823177.jpg
Format: JPEG (Joint Photographic Experts Group JFIF format)
Mime type: image/jpeg
I'm updating several thousand products and 1/3 of them have this issue. It is an official JPEG -- why doesn't Shopify let me use it?