Please make sure that your SIM card is active from the carrier company, and is inserted properly into the machine. If you determine from FAQ #8 that your 4G LTE card is MC7355, follow these steps:
Please download the driver from the link below, click on "MC7355 Driver and FW Build 4368".
Follow the installation steps and let it update. It will take some time until the update finishes, then restart the unit and try to connect again.
https://na.panasonic.com/us/support/wireless-wan-drivers-sprin