CAT_VALIDATION_ERROR_IMAGE_LINK_INVALID indicates the image_link value is missing the protocol (http/https), contains spaces or unencoded characters, or is otherwise malformed. The URL must resolve directly to a single image file, not a redirect or HTML wrapper.
Snap Catalog Manager requires product images that are publicly reachable, sized within the platform's bounds, in supported formats (JPEG/PNG typically), and free of overlays, watermarks, retailer logos, or text callouts. This issue trips when one of those constraints is broken.