GSM connection fails - NetworkManager

I am trying to achieve the gsm connection through my single board computer. I think I set up everything. Below is the output of the modem info: -------------------------------- General | dbus path: /org/freedesktop/ModemManager1/Modem/0 | device id: 10c51b4b5511adedf5c6df0380e7acab4ce64f5a -------------------------------- Hardware | manufacturer: QUALCOMM INCORPORATED | model: QUECTEL Mobile Broadband Module | firmware revision: EC25AUFAR06A01M4G | carrier config: default | h/w revision: 10000 | supported: gsm-umts, lte | current: gsm-umts, lte | equipment id: 861585041067073 -------------------------------- System | device: /sys/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.2 | drivers: option1, qmi_wwan | plugin: Quectel | primary port: cdc-wdm0 | ports: ttyUSB0 (qcdm), ttyUSB2 (at), cdc-wdm0 (qmi), wwan0 (net), | ttyUSB3 (at) -------------------------------- Numbers | own: 61451690967 -------------------------------- Status | unlock retries: sim-pin (3), sim-pin2 (0), sim-puk (10), sim-puk2 (0) | state: enabled | power state: on | signal quality: 0% (cached) -------------------------------- Modes | supported: allowed: 2g; preferred: none | allowed: 3g; preferred: none | allowed: 4g; preferred: none | allowed: 2g, 3g; preferred: 3g | allowed: 2g, 3g; preferred: 2g | allowed: 2g, 4g; preferred: 4g | allowed: 2g, 4g; preferred: 2g | allowed: 3g, 4g; preferred: 3g | allowed: 3g, 4g; preferred: 4g | allowed: 2g, 3g, 4g; preferred: 4g | allowed: 2g, 3g, 4g; preferred: 3g | allowed: 2g, 3g, 4g; preferred: 2g | current: allowed: 2g, 3g, 4g; preferred: 4g -------------------------------- Bands | supported: egsm, dcs, pcs, g850, utran-1, utran-5, utran-8, utran-2, | eutran-1, eutran-2, eutran-3, eutran-4, eutran-5, eutran-7, eutran-8, | eutran-28, eutran-40 | current: egsm, dcs, pcs, g850, utran-1, utran-5, utran-8, utran-2, | eutran-1, eutran-2, eutran-3, eutran-4, eutran-5, eutran-7, eutran-8, | eutran-28, eutran-40 -------------------------------- IP | supported: ipv4, ipv6, ipv4v6 -------------------------------- 3GPP | imei: 861585041067073 | registration: idle -------------------------------- 3GPP EPS | ue mode of operation: csps-2 -------------------------------- SIM | dbus path: /org/freedesktop/ModemManager1/SIM/0 It seems like no signal shown on Status section. And the output of the nmcli con : NAME UUID TYPE DEVICE cellular d811a35a-70fc-3716-84e1-a3578d10cc1e gsm cdc-wdm0 resin-wifi-01 a58e405d-fdc2-3649-9339-5bbaea740c76 wifi wlan0 supervisor0 8148d985-dc90-4f8c-8e38-62f83f4f13ba bridge supervisor0 And the wired thing is that the gsm is always **connecting** (not connected once): cdc-wdm0: connecting (prepare) to cellular "cdc-wdm0" gsm (option1, qmi_wwan), hw I tried to manually up the cellular: root@6f5afca:~# nmcli c up cellular Error: Connection activation failed: Network registration timed out Up to this point, I tried everything. I tested the SIM with my phone and it worked properly. I have no idea why it is not connected.