On iOS, Please ensure you have granted Meanings access to Notifications. If you denied notifications access to Meanings after it was installed, iOS prevents app developers from re-displaying the notification prompt automatically. In order to update your notification settings for a specific app, see Apple's instructions here: Change notification settings on iPhone.
For emails, please check your spam folder.
To avoid overwhelming you with excessive notifications, we send review reminder notifications at increasingly infrequent intervals if you do not complete reviews or update your vocabulary. In order to start receiving notifications again, you may need to log in and complete a review or add vocabulary to resume receiving review reminders.