Dear Chris,
First of all, many thanks for making this amazing course format available to the community. It looks great in our Moodle environment!
Unfortunately I am having a similar issue with the email digest not working. I've checked the course settings, and made sure that Enable notifications is set to Yes. Then on the course page I've also chosen Edit notification settings and set the Notification Type to Per digest. I've also changed it to Each post, just to see if it makes a difference. Unfortunately it does not.
We are running Moodle 2.8.7 and all other email digest options (forums, etc) are performed as normally and work really well.
Any help would be most welcome, thanks again for this amazing course format!