There are several possibilities as to why you didn't receive a notification.
1. Spam Blocker. You might have Spam Blocker software installed on your email system. Make sure you can receive emails from firstname.lastname@example.org.
2. No notification sent by member. The member may have chosen to not send emails to guests on that specific update.
3. Personal preferences set to not receive notifications. To change your preferences, go to Profile located in the drop-down menu under your name in the upper right side. In the My Info tab, scroll down to the Preferences section and check the box that says you want to receive email notifications. Click Save Changes and now you will receive email notifications when the member posts an update.