Sierra Wireless EM7345 4G LTE - can't connect

[Krzysztof Klimonda]

Hey,
  I'm having a problem trying to the aforementioned modem to work
under Linux. I'm currently running Debian sid, libmbim 1.10.0,
ModemManager from git master, Kernel 3.16-rc6.
  First, when I booted the system the wwan0 interface wasn't created
at all, only after loading cdc_ncm with prefer_mbim=Y did it show up.
  However, trying to connect to the network failed. running mmcli -m 0
--simple-connect=apn=www.plusgsm.pl fails with an "error: couldn't
connect the modem:
'GDBus.Error:org.freedesktop.libmbim.Error.Status.Failure:
Failure'"message. it works fine with the same SIM card and an external
USB modem though.
  I've attached a debug log from ModemManager that is being generated
when I run that command.
Any ideas how to debug it further?
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