Here is a list of steps you can take to fix issues with mobile data or cellular network:

1. Check your coverage data: Make sure that your device is connecting to indended network. Connect to a recent network that you have connected to before.
2. Restart your device in normal mode: It is advisable to completely shutdown mode on your device before attempting a restart. It will help refresh your network connections.
3. Check your settings: Make sure your device settings are set correctly and updated to the latest version. This includes Data Roaming, Airplane Mode etc.
4. Check data limits: Ensure that you have enough data left to use, or have access to an updated/upgrade data plan. Check for any additional data features.
5. Check for service outages: Check for any areas with network or data issues. Your carrier may be experiencing unexpected outages in certain areas.
6. Update your device software: Ensure your device os is updted to the latest version. Use the update settings on your device or go to your device manufacture’s website for further instructions.