Ah, now that I can see around the Photon links, I think I know what’s going on. It looks like your images are coming from a different domain. This is problematic for the plugin because it relies on information in your WordPress database to accurately serve up the correct image files.
So you can try to add this to your site, either in your theme’s functions.php file or in a functionality plugin if you have one:
add_filter( 'send_images_rss_process_external_images', '__return_true' );
Now, this has limitations. It will add an inline style to each image to attempt to force it to display at the width of the email, but that varies in effectiveness based on the email client.
Your featured images, however, are hosted on this domain, and since you mention above that you are wanting to generate a post excerpt newsletter, what about changing your feed output to Summaries instead? Your feed will then include the featured image, at whatever size you pick, and approximately the first 75 words of your post (it may be more/less as it tries to cut off at the end of a sentence). You can also hand craft an excerpt, using the built in WordPress excerpt functionality, rather than relying on the plugin to measure.
You might check out this really fabulous tutorial (which I did not write, but wish I had) for help setting up the excerpts for MailChimp, but it should be fairly straightforward. You would also want to go ahead and turn off the alternate feed, since it’s for full text feeds only.
I think that setting up your feed for excerpts only may be your best bet, since your images are hosted off your domain, and due to the length of your posts. It will give you the most complete control over your readers’ experience as well.
I hope that helps–please let me know how it goes. If you need me to look more in depth, please contact me directly and we can go from there.
