3G connection with ModemManager and Netplan connect and disconnect immediatly

I have a problem with an old 3G modem (Telit HE910), the connection is made via Netplan and ModemManager. The modem is recognized correctly when Ubuntu starts and the SIM is also recognized without problems. The strange thing is that it seems that the connection is established but then immediately the modem disconnects. I tried starting ModemManager in debug mode but I'm not very expert with modems to understand where the problem actually is. Netplan config: network: version: 2 renderer: NetworkManager ethernets: enp3: # eth0 - Maintenance dhcp4: false optional: true addresses: - 172.0.0.10/24 routes: - to: default via: 172.0.0.1 nameservers: addresses: - 8.8.8.8 - 8.8.4.4 dhcp4-overrides: route-metric: 1 match: name: enp3* set-name: enp3 enp4: # eth1 - External modem dhcp4: true dhcp6: false optional: true match: name: enp4* set-name: enp4 modems: telit: # Internal modem dhcp4: true optional: true apn: iliad auto-config: true dhcp4-overrides: route-metric: 900 match: name: ttyACM* set-name: mobile wifis: wlp1s0: dhcp4: false dhcp6: false optional: true access-points: # Required for wifis "empty": password: "" ModemManager logs: ModemManager: [1662750117.761616] [modem0/bearer0] connection through a plain serial AT port: ttyACM0 ModemManager: [1662750117.761825] [modem0/ttyACM0/at] device open count is 5 (open) ModemManager: [1662750117.762137] [modem0/ttyACM0/at] device open count is 4 (close) ModemManager: [1662750117.762428] [modem0/ttyACM0/at] --> 'ATD*99***3#' ModemManager: [1662750117.796882] [modem0/ttyACM0/at] CONNECT' ModemManager: [1662750117.797202] [modem0/bearer0] setting flow control in ttyACM0: rts-cts ModemManager: [1662750117.797369] [modem0/ttyACM0/at] enabling RTS/CTS flow control ModemManager: [1662750117.797575] [modem0/ttyACM0/at] flow control settings updated to rts-cts ModemManager: [1662750117.797780] [modem0/ttyACM0/at] port now connected ModemManager: [1662750117.798010] [modem0/bearer0] connected ModemManager: [1662750117.798634] [modem0/bearer0] PPP is required for connection, will ignore disconnection reports ModemManager: [1662750117.798836] [modem0] state changed (registered -> connected) ModemManager: [1662750117.800684] [modem0] simple connect state (8/8): all done ModemManager: [1662750117.801266] [modem0/ttyACM0/at] device open count is 3 (close) ModemManager: [1662750117.836536] [modem0] user request to disconnect modem (all bearers) ModemManager: [1662750117.839942] [modem0] user request to disconnect modem (all bearers) ModemManager: [1662750117.850015] [modem0] user request to connect modem ModemManager: [1662750117.859771] [modem0/bearer0] disconnecting... ModemManager: [1662750117.860051] [modem0] state changed (connected -> disconnecting) ModemManager: [1662750117.861365] [modem0/bearer0] sending PDP context deactivation in secondary port... ModemManager: [1662750117.861621] [modem0/ttyACM3/at] device open count is 2 (open) ModemManager: [1662750117.862099] [modem0/ttyACM3/at] --> 'AT+CGACT=0,3' ModemManager: [1662750117.888064] [modem0/ttyACM3/at] OK' ModemManager: [1662750117.888482] [modem0/bearer0] reopening data port ttyACM0... ModemManager: [1662750117.888661] [modem0/ttyACM0/at] reopening port (3) ModemManager: [1662750117.888796] [modem0/ttyACM0/at] device open count is 2 (close) ModemManager: [1662750117.888921] [modem0/ttyACM0/at] device open count is 1 (close) ModemManager: [1662750117.889047] [modem0/ttyACM0/at] device open count is 0 (close) ModemManager: [1662750117.889250] [modem0/ttyACM0/at] closing serial port... ModemManager: [1662750117.889431] [modem0/ttyACM0/at] port now disconnected ModemManager: [1662750117.892280] [modem0/ttyACM0/at] serial port closed ModemManager: [1662750117.892472] [modem0/ttyACM3/at] device open count is 1 (close) ModemManager: [1662750117.892880] [modem0] simple connect started... ModemManager: [1662750117.893018] [modem0] profile ID: unspecified ModemManager: [1662750117.893149] [modem0] PIN: unspecified ModemManager: [1662750117.893266] [modem0] operator ID: unspecified ModemManager: [1662750117.893376] [modem0] allowed roaming: yes ModemManager: [1662750117.893487] [modem0] APN: iliad ModemManager: [1662750117.893596] [modem0] APN type: unspecified ModemManager: [1662750117.893707] [modem0] IP family: ipv4v6 ModemManager: [1662750117.893828] [modem0] allowed authentication: unspecified ModemManager: [1662750117.893948] [modem0] user: unspecified ModemManager: [1662750117.894068] [modem0] password: unspecified ModemManager: [1662750117.894184] [modem0] multiplex: unspecified ModemManager: [1662750117.894341] [modem0] simple connect state (4/8): wait to get fully enabled ModemManager: [1662750118.893991] [modem0/ttyACM0/at] opening serial port... ModemManager: [1662750118.896308] [modem0/ttyACM0/at] setting up baudrate: 57600 ModemManager: [1662750118.896488] [modem0/ttyACM0/at] no flow control explicitly requested for device ModemManager: [1662750118.896831] [modem0/ttyACM0/at] device open count is 1 (open) ModemManager: [1662750118.896970] [modem0/ttyACM0/at] device open count is 2 (open) ModemManager: [1662750118.897117] [modem0/ttyACM0/at] device open count is 3 (open) ModemManager: [1662750118.897306] [modem0/bearer0] flashing data port ttyACM0... ModemManager: [1662750118.897691] [modem0/ttyACM0/at] [1662750118.898171] [modem0/ttyACM0/at] device open count is 2 (close) ModemManager: [1662750118.898562] [modem0/ttyACM0/at] running init sequence... ModemManager: [1662750118.899053] [modem0/bearer0] PDP disconnection already sent ModemManager: [1662750118.899235] [modem0/bearer0] disconnected ModemManager: [1662750118.899435] [modem0] state changed (disconnecting -> registered) ModemManager: [1662750118.899820] [modem0] simple connect state (5/8): register ModemManager: [1662750118.900457] [modem0] already registered automatically in network '22250', automatic registration not launched... ModemManager: [1662750118.902789] [modem0/bearer0] connection #1 finished: duration 1s, tx: 0 bytes, rx: 0 bytes ModemManager: [1662750118.903778] [modem0] simple connect state (6/8): bearer ModemManager: [1662750118.905370] [modem0] creating new bearer... ModemManager: [1662750118.905609] [modem0] creating broadband bearer in broadband modem... ModemManager: [1662750118.906852] [modem0/ttyACM0/at] device open count is 3 (open) ModemManager: [1662750118.910141] [modem0] simple connect state (7/8): connect ModemManager: [1662750118.910928] [modem0/bearer1] connecting... ModemManager: [1662750118.911186] [modem0] state changed (registered -> connecting) ModemManager: [1662750118.913608] [modem0/bearer1] launching 3GPP connection attempt ModemManager: [1662750118.913857] [modem0] set profile state (1/8): check format ModemManager: [1662750118.914074] [modem0/ttyACM0/at] device open count is 4 (open) ModemManager: [1662750118.914341] [modem0/ttyACM0/at] device open count is 3 (close) ModemManager: [1662750118.915863] [modem0/ttyACM0/at] --> 'ATE0' ModemManager: [1662750119.795226] [modem0/ttyACM0/at] [1662750120.795152] [modem0/ttyACM0/at] [1662750121.180951] [modem0/ttyACM3/at] +CIEV: signal,2' ModemManager: [1662750121.181451] [modem0] signal quality updated (28) ModemManager: [1662750121.795367] [modem0/ttyACM0/at] [1662750122.510824] [modem0/ttyACM0/at] device open count is 4 (open) ModemManager: [1662750122.511330] [modem0/ttyACM0/at] --> 'ATV1' ModemManager: [1662750122.795777] [modem0/ttyACM0/at] [1662750123.795760] [modem0/ttyACM0/at] [1662750124.796161] [modem0/ttyACM0/at] [1662750125.510748] [modem0] port ttyACM0 timed out 2 consecutive times ModemManager: [1662750125.511081] [modem0/ttyACM0/at] --> 'AT+CMEE=1' ModemManager: [1662750125.796557] [modem0/ttyACM0/at] [1662750126.797186] [modem0/ttyACM0/at] [1662750127.797395] [modem0/ttyACM0/at] [1662750128.511090] [modem0] port ttyACM0 timed out 3 consecutive times ModemManager: [1662750128.511364] [modem0/ttyACM0/at] --> 'ATX4' ModemManager: [1662750128.931528] [modem0/ttyACM0/at] NO CARRIER' ModemManager: [1662750128.931900] [modem0/ttyACM0/at] operation failure: 1 (No carrier) ModemManager: [1662750128.932274] [modem0/ttyACM0/at] --> 'AT&C1' ModemManager: [1662750128.938206] [modem0/ttyACM0/at] +CIEV: signal,2' ModemManager: [1662750128.938646] [modem0] signal quality updated (28) ModemManager: [1662750128.948414] [modem0/ttyACM0/at] OK' ModemManager: [1662750128.949130] [modem0] +CGDCONT format details for PDP type 'ipv4v6': minimum 1, maximum 5 ModemManager: [1662750128.949320] [modem0] context definition format: minimum 1, maximum 5 ModemManager: [1662750128.949464] [modem0] set profile state (2/8): list before ModemManager: [1662750128.949675] [modem0/ttyACM0/at] device open count is 5 (open) ModemManager: [1662750128.949897] [modem0/ttyACM0/at] device open count is 4 (close) ModemManager: [1662750128.950154] [modem0/ttyACM0/at] --> 'AT+CCLK?' ModemManager: [1662750128.975347] [modem0/ttyACM0/at] ' ModemManager: [1662750128.975784] [modem0/ttyACM0/at] OK' ModemManager: [1662750128.976535] [modem0/ttyACM0/at] device open count is 3 (close) ModemManager: [1662750128.977418] [modem0/ttyACM0/at] --> 'AT+CGDCONT?' ModemManager: [1662750129.003874] [modem0/ttyACM0/at] +CGDCONT: 1,"IP","web.omnitel.it","",0,0+CGDCONT: 2,"IP","iliad","",0,0+CGDCONT: 3,"IPV4V6","iliad","",0,0OK' ModemManager: [1662750129.004954] [modem0] set profile state (3/8): select profile (best) ModemManager: [1662750129.005130] [modem0] found exact context at profile 3 ModemManager: [1662750129.005258] [modem0] reusing profile '3' ModemManager: [1662750129.005408] [modem0] set profile state (4/8): check activated profile ModemManager: [1662750129.005614] [modem0] checking if profile with id '3' is already activated...= ModemManager: [1662750129.005813] [modem0/ttyACM0/at] device open count is 4 (open) ModemManager: [1662750129.006106] [modem0/ttyACM0/at] device open count is 3 (close) ModemManager: [1662750129.006645] [modem0/ttyACM0/at] --> 'AT+CGACT?' ModemManager: [1662750129.032246] [modem0/ttyACM0/at] ' ModemManager: [1662750129.032967] [modem0/ttyACM0/at] +CGACT: 2,0+CGACT: 3,0OK' ModemManager: [1662750129.034446] [modem0] profile '3' is not activated ModemManager: [1662750129.034826] [modem0] set profile state (6/8): profile already stored ModemManager: [1662750129.035450] [modem0] set profile state (8/8): all done ModemManager: [1662750129.036522] [modem0/ttyACM0/at] device open count is 4 (open)