Android app works only on wifi not on mobile network 3g

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http://stackoverflow.com – I am developing an Android App (minimum android 8 , max 16) . I'm testing this app on my Samsung Galaxy Note2 . The app is doing some php parsing (login to the database) through Internet. It uses android.manifest.INTERNET permission , and android.manifest.ACCES_FINE_LOCATION permission. When on WIFI Networks , it works as it should work , but when i try to use Mobile Data (3G) , the app gets stuck and "force-closes" when i click my "Login" button in it. (the server's database is accesible from "web browsers" from both wifi and 3g network.) I can't realise why this is happening :|. Anyone h (HowTos)