"port not candidate" error message with DELL Wireless 5570 (aka Sierra Wireless AirPrime 7W5P6)

[Giuseppe Sacco]

Hello to all,
I am not at all an expert of modem manager but I hope this is the right
place where to post my question.

I am trying to use a WWAN module on a laptop. The module is named "Dell
Wireless 5570 HSPA+ (42Mbps) Mobile Broadband Card" (a.k.a. Sierra
Wireless AirPrime 7W5P6).

It is listed like this:

$ lsusb --verbose -d 413c: | head -17

Bus 003 Device 003: ID 413c:81a3 Dell Computer Corp. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  idVendor           0x413c Dell Computer Corp.
  idProduct          0x81a3 
  bcdDevice            0.06
  iManufacturer           1 Sierra Wireless, Incorporated
  iProduct                2 Dell Wireless 5570 HSPA+ (42Mbps) Mobile Broadband Card
  iSerial                 3 
  bNumConfigurations      2


The card is not used by modemmanager, in fact I does write:

ModemManager[7979]: <debug> [1592288162.080686] (usbmisc/cdc-wdm0):
adding device at sysfs path:
/sys/devices/pci0000:00/0000:00:1d.0/usb3/3-1/3-1.6/3-
1.6:2.12/usbmisc/cdc-wdm0
ModemManager[7979]: <debug> [1592288162.080759] (usbmisc/cdc-wdm0):
port not candidate


This happens even if I run ModemManager after putting the card online
with this command:
$ sudo qmicli -d /dev/cdc-wdm0 --dms-set-fcc-authentication
and checking the results this way:
$ sudo qmicli -d /dev/cdc-wdm0 --dms-get-operating-mode
[/dev/cdc-wdm0] Operating mode retrieved:
	Mode: 'online'
	HW restricted: 'no'

Is it possible to use modemmanager for managing this card?

Thank you,
Giuseppe