Do you get the same result when you import just that one line?
The URL must exactly match the image URL in the WordPress media library. Is the image in the media library? If you clikc ‘edit’ under the image, is that URL the same as listed in the ‘file URL’ field for the image?
You can also try these formats:
If that doesn’t work, please feel free to send a login (my email is chrisvrichardson at mappresspro.com) and I’ll be happy to take a look for you.