The ISBN in Koha do matches the ISBN in Amazon.

I can at least confirm that I see the same result: For that particular ISBN the image doesn't load. For others it does. I don't see how it could be caused by anything within Koha. As far as I can tell the problem is that Amazon isn't serving up the image at the expected address. Since we're not paying Amazon for the service I don't think we can complain if it occasionally fails. -- Owen -- Web Developer Athens County Public Libraries https://www.myacpl.org