CBC Issue: ASUS Chromebook C300MA stopped finding Verizon mobile network ( https://goo.gl/3TYkLf )

OP sent report (via alt+shift+I) with "@elizabeth" in the description.

#CBC-RS/TC-watchlist

Notes from my debugging of the issue on my chromebook:

1.  checked and device (LTE modem) is always enumerated correctly -dmesg output:

  2.681114] usb 1-2.2: New USB device found, idVendor=216f, idProduct=0047
[    2.681125] usb 1-2.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[    2.681130] usb 1-2.2: Product: 'Alt3100 devboard'
[    2.681134] usb 1-2.2: Manufacturer: 'Altair Semiconductor'
[    2.681138] usb 1-2.2: SerialNumber: usb_serial_num_0
[    2.689447] cdc_ether 1-2.2:1.0 eth0: register 'cdc_ether' at usb-0000:00:14.0-2.2, CDC Ethernet Device, 00:11:22:33:44:56
[    2.693283] cdc_acm 1-2.2:1.2: ttyACM0: USB ACM device




2. Network device info:


1. network device info - I removed phone number & IMEI for security reasons.

/device/eth0
  Address: 001122334456
  Cellular.APNList/0/0/apn: vzwinternet
  Cellular.APNList/0/1/name: 4G LTE Contract
  Cellular.AllowRoaming: false
  Cellular.Carrier: 
  Cellular.ESN: 
  Cellular.Family: 
  Cellular.FirmwareRevision: LTEUSB_02_04_05_10_61
  Cellular.HardwareRevision: 
  Cellular.HomeProvider/0/code: 311480
  Cellular.HomeProvider/1/country: us
  Cellular.HomeProvider/2/name: Verizon Wireless
  Cellular.ICCID: xxx (<==I erased this for security reason)
  Cellular.IMEI: xxx (<== I erased this for security reason)
  Cellular.IMSI: xxx (<==I erased this for security reason)
  Cellular.MDN: xxx (<== I erased this for security reason)
  Cellular.MEID: 
  Cellular.MIN: 
  Cellular.Manufacturer: Altair Semiconductor
  Cellular.ModelID: ALT3100
  Cellular.PRLVersion: 0
  Cellular.ProviderRequiresRoaming: false
  Cellular.SIMLockStatus/0/LockEnabled: false
  Cellular.SIMLockStatus/1/LockType: 
  Cellular.SIMLockStatus/2/RetriesLeft: 3
  Cellular.SIMPresent: true
  Cellular.SelectedNetwork: 
  Cellular.SupportNetworkScan: false
  DBus.Object: /org/freedesktop/ModemManager1/Modem/0
  DBus.Service: org.freedesktop.ModemManager1
  Interface: eth0
  Name: eth0
  Powered: true
  ReceiveByteCount: 0
  ScanInterval: 0
  Scanning: true
  SelectedService: /
  TransmitByteCount: 0
  Type: cellular




2. Modem status shows signal level as 0 and LTE bands don't look correct.

crosh> modem status

Modem /org/freedesktop/ModemManager1/Modem/7:
  GetStatus:
    state: 7
  Properties:
    Sim: /org/freedesktop/ModemManager1/SIM/7
    SupportedCapabilities: 8
    CurrentCapabilities: 8
    MaxBearers: 1
    MaxActiveBearers: 1
    Manufacturer: Altair Semiconductor
    Model: ALT3100
    Revision: LTEUSB_02_04_05_10_61
    HardwareRevision: 
    DeviceIdentifier: 6d84f03b5961ab4fac29f566e0d7e1d68ca625fd
    Device: /sys/devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2.2
    Drivers: cdc_ether, cdc_acm
    Plugin: Altair LTE
    PrimaryPort: ttyACM0
    Ports: ttyACM0, 3, eth0, 2
    EquipmentIdentifier: 356585063620611
    UnlockRequired: 1
    UnlockRetries: 3, 3, 10, 10
    State: 7
    StateFailedReason: 0
    AccessTechnologies: 0
    SignalQuality: 0, false  <=== always shows as 0, false
    OwnNumbers: +1XXXXXXXXXX
    PowerState: 3
    SupportedModes: 4294967295, 0
    CurrentModes: 4294967295, 0
    SupportedBands: 34, 43  <=====
    CurrentBands: 43
    SupportedIpFamilies: 7


4.Another user experiencing the same issue narrowed down the problem to Chrome OS upgrade version. He said -

"After the upgrade to chromeOS 63.0.3239.140 I couldn't connect over the mobile network (3G/4G)."

"Finally I reverted to chromeOS 62.0.3202.97 and I could again connect over the mobile network."

So I am requesting google team to focus on the diff between the above two version and focus on the Altair modem related files/changes. I am sure the root cause is there to be found and fixed.

Thanks.
SF

(Bulk Edit) Adding the new conops Chrome OS hotlist to all open issues with the "#CBC-RS/TC-watchlist" tag, our former tracking tag.