If the SIM card is inserted correctly, you should see you should see a valid “Network” listed and “Service state” when you look at
Settings-> About Tablet -> Status
Most SIMs provide a notification that “SIM is not provisioned” if they are invalid. But it is always best to check with your carrier on the validity of the SIM.
If phone number is listed as unknown, here are some troubleshooting tips:
Check if baseband version is listed correctly or unknown.
Check if device is camped and registered on network.
Check if you are able to manually search for networks.
For expert users, there are two ways to check inside adb shell
echo -e "AT+CPIN?\r\n" > /dev/ttyACM2 && cat /dev/ttyACM2
Must see READY here as response.
echo -e "AT+CNUM\r\n" > /dev/ttyACM2 && cat /dev/ttyACM2
must see phone number listed here as response
Verizon and Sprint are currently unsupported in the US.
Carrier must provide 2G, 3G, or LTE Network. CDMA/EV-DO based networks are not supported.