I’m attaching this link to an Ubuntu bug report discussing the Verizon Wireless USB551L 4G Wireless Card:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/886130
This may (or may not) be relevant to your situation. It appears as if the device needs to be in the correct state before it will be recognised as a NIC correctly (supported by the cdc_ether kernel module).
You haven’t shared with us if anything special was ever needed to get this device up and running (beyond network manager configuration).