Cellular Hologram.io issues

A member of our team has had success using the same modem as you.
Can you try using a development os edition and connecting it to Wifi/Ethernet.
You can then use the webterminal to acess the HostOS and run mmcli -L to check that the modem has been discovered.
Additionally, running journalctl -u ModemManager --no-pager in the HostOS will provide some additional information as to what is going on here.