ModemManager: Connecting to cellular mobile network not possible

Publication date: 2025-08-18

Issue: Connecting to the cellular mobile network via Network Manager failed

Network Manager makes configuring the connection and establishing the connection convenient. However, it did not work, the connection did not come up.

Error messages like Invalid transition and [modem0] Busy can be found.

As ModemManager is used in the background, we can attempt to establish the connection on the command line as follows:

mmcli -m 0 -e

This yielded the following error:

error: couldn't enable the modem: 'GDBus.Error:org.freedesktop.ModemManager1.Error.Core.Retry: Invalid transition'

Solution: Remove FCC lock

Internet search revealed the following one-liner to remove the FCC lock:

ln -sft /etc/ModemManager/fcc-unlock.d /usr/share/ModemManager/fcc-unlock.available.d/*

Afterwards, everything worked well, tested with:

mmcli -m 0
mmcli -m 0 -e

Hint towards the solution

FCC unlock procedure https://modemmanager.org/docs/modemmanager/fcc-unlock/
Ubuntu 22.04 Lenovo T14 Gen 4 modem enable https://askubuntu.com/questions/1516501/ubuntu-22-04-lenovo-t14-gen-4-modem-enable-gdbus-errororg-freedesktop-modemmana