Did you enable and start ModemManager.service
Edit:
systemctl enable ModemManager.service
systemctl start ModemManager.service
Edit2: You can also check
systemctl status ModemManager.service
Then try
mmcli -L
Did you enable and start ModemManager.service
Edit:
systemctl enable ModemManager.service
systemctl start ModemManager.service
Edit2: You can also check
systemctl status ModemManager.service
Then try
mmcli -L