I am not receiving Push Notifications/Messages.
If you said "no" to notifications when asked when the app launched after you first installed it, the notifications will not go to your phone.
However, you can turn them back on.
For Apple go to Settings -> Notification Center -> scroll down to the app and make sure the notifications are on or "alert" or "banners"
For Android, Settings -> Application manager -> Choose app -> check box for "show notifications".
Also, sometimes it takes a few hours for a newly downloaded app to start receiving push notifications if you had just installed it.