We've been having our technicians look into this and so far they have found members who reported email as spam and were unsubscribed, members who opted out of receiving email notifications, and other things that have caused our system to stop sending them emails.
We'll continue to do all we can on our side to get the emails through to our members, but our members need to be diligent at making sure they don't mark our emails as spam, unsubscribe, opt-out, etc., especially if they want to keep getting them.