Your drivers were not successfully installed or detected by the installation. Try installing the firmware update on a different USB port or on another computer.
You can confirm if the drivers are successful by looking under your Device Manager in the Modems and Network Adapters sections. If the drivers were successful there will be a Novatel Wireless device listed in each category and they will remain there when your MiFi is USB connected. Only when Device Manager can see your devices will your firmware update be able to complete.