simple fix for me was the following:I am having this problem too, hard reset doesn't fix it...Could be a back end provisioning issue. I was told this at the store. If it doesn't clear up by Monday, I will go back.
Follow the troubleshooting steps below to resolve data connection issues:
1.Remove the SIM card and leave the SIM card out for the next three steps.
2.Perform a Master Reset (Settings > About).
3.Let the product boot up without a SIM card.
4.Turn off the device.
5.Verify that the SIM card is LTE enabled.
6.Insert SIM card and boot up.