There are two settings to check for this.
1) Within MobileDay, go to menu> Meeting Notifications and specify how long you would like to be notified prior to your meetings. Make sure this isn't set to "Never". Your choices are:
2) If the notifications are set to a time period other than "Never", then please also check under Android settings to make sure that notification content is selected as ON when the device is locked.
To do that go to Settings > Sound and Notification, under the "Notification" heading tap "When device is locked" and of the options tap "Show all notification content".