- Setup a default mobile data configuration settings, go to Settings > configuration, and select your network operator.
- Confirm with your network operator that you have an active mobile data subscription (access to internet) on your SIM card.
- Enable the mobile data connection on your phone, go to Settings > connectivity > mobile data and switch mobile data to On (check that your data roaming is activated when you are not in your home network).
The previous actions usually solve your problem. If it does not help, insert your SIM card in another device and retry. If it is working in another device, contact your network operator for Internet settings reconfiguration or you may need reset the phone settings (Menu > Settings > Restore factory sett. > Settings only).