This error appears when JIG initially thought there was content to show (and found some), but when gathering a list of thumbnails it ruled all of them out. The cause may be:
- When using WPML: all of the posts are in a different language. Either translate all articles or use the duplicate feature in WPML to maintain a placeholder until translation is complete. JIG will not show content in other languages than the currently selected. This is also the default behavior of WPML.
- When using RSS feeds: while there are articles in the feed, none of them contains a valid thumbnail. It could be that the thumbnails are added in an unsupported way. Read more at the fix for RSS feeds don’t work. If your feed URL starts with https, then this may be of help: SSL errors.
- Otherwise, the size of the images could not be determined. It's necessary for the justified layout to work. When working with remote sources, CURL loads a portion of the image and the GD library is used to determine its size. Please ensure that you have GD library installed - when in doubt, ask your hosting's support.