No images showing with Send images to RSS

I see that the plugin is adding the featured image on your development site feed, at least for the main RSS feed.

I’m not familiar with Libsyn, but I expect it does its own feed modifications as well, so it could be that for your podcast feed, that it is overriding the modifications made by Send Images to RSS. This plugin uses the WordPress featured image, or an image uploaded to the post. Since Libsyn looks like it has its own system set up for managing podcast entries, and says that media files are hosted there, not within WordPress, it may be that this plugin will not work with the Libsyn podcast feed.

Actually, on your development site, two images are being added to each entry in your RSS feed–one is from Send Images to RSS, but the other one could be added by your theme or another plugin.