No email notice when member tagged in a post with @nicename

When I tag a member with the @nicename that appears under their avatar, I get all the email notices about creating the topic, etc, but no email to the tagged user is sent.

Is there maybe a WP setting that interferes? I've found in setting up my WP-Foro site, some of the settings issues I've run into are because the regular WP site settings are overriding WP-Foro's…. Or is there a WP-Foro place I need to activate this function?

The hover text suggests this should be an automatic feature that "just works".

Thank you for advice!
holly