BuddyPress.org

Hi there, here’s the steps I would take:

Deactivate all other plugins.
Switch to 2017 theme and test
Check for changes to functions.php, wp-config.php, bp-custom.php ( if you have one ) basically any place where custom scripts could be hiding.
Try recreating your emails in the Tools>>BuddyPress admin page.
If they still don’t work
Enable WP-DEBUG, install Query Monitor plus an error log viewer. initiate some emails and see if you get any errors at the same time.