You should use the carrier specific firmware when available. If not available, and you are using the Generic firmware, you may have to configure the carrier’s APN before the modem will connect. Most carriers publish a FAQ for APN settings.
Configure the APN using Skylight
Windows users can download and install Skylight Connection Manager from Sierra Wireless for better connection management. Skylight is not available for other operating systems.
Configure the APN using Windows
If you are using Windows 7, you should use Skylight. If you are using Windows 8 or 10, you may use the Windows connection manager by clicking the network icon (“PC and cable” or “signal bars”) in the system tray and selecting Network Settings, then clicking the cellular network connection in the new window and selecting the option for APN settings.
Alternatively users can navigate to Settings -> Network & Internet