Photon is an image acceleration and editing service for sites hosted on WordPress.com or on Jetpack-connected WordPress sites. The Photon plugin generates external urls for each image and hence the Aqua thumb resizer cannot handle the same ( security reasons behind this). This can make images to not appear on blogs, portfolio pages and the shortcodes do not display images. If this plugin is deactivated, things work fine irrespective of the thumbnail generation method chosen.
To make things work with Jetpack Photon plugin, will need to make a couple of minor changes –
1) Change the thumbnail generation method from Aqua to WordPress in the General tab in theme options. Choosing Aqua will make the image resizing to fail if you have Photon enabled.
2) Make the following code change in the file framework/presentation/layout-manager.php – line number 392 from
$thumbnail_size = mo_get_wp_image_size($image_size, 'medium'); // default to medium if size is invalid