I finally figured it out – only because I posted here for help. Murhpy’s law, you know how it goes.
I have another addon that lets me enter a URL on the image files. I enter the URL on some of them for use when featured for this other addon. It turns out, the URL on that image file was overriding the URL for the Feast plugin if it used the same featured image.
I’d like to add a little more information. When I sign up, I do receive the email to confirm the subscription. I confirm it and get another followup email. However, I am not getting email notifications that a new article was posted.