My name is Rae and I work for Shopify. Welcome to the Community forums!
When you receive this error, are you adding these images from a URL, or by uploading a file?
If you're using a URL, it's possible that the link to the image you're trying to use no longer exists at its original location. If this is the case, this workaround can help resolve things:
Alternatively, once the image is saved to your computer, you may also wish to upload the image directly to your product by following the first point under step 3 here. If you decide to do this, it's still important to ensure the image doesn't exceed Shopify's upload limits.
Please give these steps a try, and keep me posted on how it goes!
Thanks for getting back to me. I'm glad to hear that you've been in contact with our team about this via email, too.
Have you also had a chance to try uploading images from a computer instead? Give this a try and let me know if you run into the same issue.
I hope to hear back from you soon!