Nokia Lumia 1520 - I cannot connect to the internet using a mobile data connection on my Lumia phone

  1. Setup a default mobile data internet access point. Go to Settings > access point, and select your network operator or enter new (+) APN settings related to internet and/or MMS as needed. Confirm the selection by pressing Done at the bottom of the screen. (Note: You can only edit APN settings which have been manually configured).
  2. Confirm with your network operator that you have an active mobile data subscription (access to internet) on your SIM card.
  3. Enable the cellular data connection on your phone. Go to Settings > cellular and switch Data connection to On.
  4. Check that your data roaming is activated when you are not in your home network. Go to Settings > cellular and select data roaming options.
  5. If the data connection is lost, try reconnecting by switching Flight mode on and back off: Tap Settings > Flight mode. This resets the active data connection.

If the above steps do not help, insert your SIM card in another device and retry. If it works in another device, contact your network operator for Internet settings reconfiguration.