When you use NB-IoT module and run the command AT+CSG=99,99. It means the device doesn't attached to the NB-IoT network. If attached to network, the first 99 should be 2~31.
Below is the definition for the AT+CSQ
CSQ Definition
In this case, you can check:
- Whether the antenna connection is good.
- Whether you use a valid SIM Card
- Whether you the SIM card place correctly.
- Whether the NB-IoT Network you use match the End Device Module support network.
- Whether you have select the correct band for your operator. See Specify_NB-IoT_Band