Image Styles Broken?
This should be a folder permission issue. What you need to do is check the image style folder (sites/all/default/files/styles) if it is writable. You can use ls command to check the directory permission. To change the permission you either need chmod or chown commands to make the folders writable by Drupal.

Once the permission are correct you may need to flush the cache for images. If you have Drush you can do that by running drush image-flush STYLE_NAME or by clearing them all by running drush image-flush all.