I am also having this problem. I am able to send admin notifications to the group I have set up, and those arrive successfully. However activity notification, such as forum topics, updates to topics you’ve started, new members, etc, is not arriving in any format.
I’ve noticed that while on the front end of the site, when I change people’s email setting, it shows as “daily digest” on the front end, but when I look at the settings in the WP Admin area, they are set as “None”. Guessing this might be related to the issue.
I am using the most recent version of the plugin, Buddypress, and WordPress. If there’s anything I can give you, facts wise, that will help chase it down, please let me know. I am unfortunately not a PHP wiz yet, or I’d do more.
Hoping to use this in a client’s set up, so hopefully we can all work together to solve the problem soon. Thanks in advance for your time and work!