Navigate to Settings-> More-> Mobile Networks. There is a checkbox for "data enabled." Make sure it has a tick by it to confirm data is enabled. If data is enabled and is working, you will see your RAT (3G/4G/2G/LTE/H) icons on top of the signal strength bar on the top right corner in the GUI. Another way to check is to navigate to Settings-> About Tablet-> Status. The mobile network state must say “connected”.