Maybe your cellular data is turned off? I don't have an android or Samsung but here are some instructions from Verizon.
1. From a Home screen tap Apps Apps icon .
(Note These instructions apply to Standard mode only.)
2. Tap Settings.
3. Tap Data usage.
4.T ap Mobile data to turn on On indicator or off Off indicator.
Instructions taken from: https://www.verizonwireless.com/support/knowledge-base-175818/