It coluld be a few issues
Issue one: Poor signal strength
If the network signal strength is poor, you may not be able to receive calls or texts, to improve the signal, please move to a area with better signal.
Issue two: Message Centre Number missing or incorrect.
If the message center Number is missing or incorrect this will effect messaging capabilities. Go to messages app > ... > Settings > more settings > Text messages. And make sure you message center no is correct. (Google for more info).
Issue 3: The app may need a update, check the galaxy store > Menu > Updates > Update All to update any apps
Go to settings app > Software update > download and install. For system updates.
If the app still wont work, try resseting by long pressing the app icon > app info > storage > detlte the cache and data. Then try the app again.
Let me know how you get on...
