Just to add to this, here’s the other thread I mentioned, with the screenshot I can’t explain.
By the way, as well as understanding why these eMails are not being sent, I’m also curious to know if there is a way to manually resend a digest eMail to a particular contact. I basically want to get their attention again, via Discourse, since it appears nothing is doing so at this point (though it should, according to their settings).