Usually, there are 3 reasons for this:
1) Emails are going to junk, spam or to the "promotions" tab. Make sure you mark them as "safe", so they'll be directed to your main inbox.
2) You may have unsubscribed from our emails. Send an email to email@example.com explaining the situation. We'll take care of it right away!
3) There may have been a typo and the notification email is wrong. Note that the login email is not necessarily the same email that you chose to receive notifications.
Make sure you're checking the right email address. Go to "edit profile" and on the left-hand side, change "the best email to receive notifications" if you have to.