- Please check the troubleshooting section.
https://docs.neqto.com/docs/en/spresense-series/software/initial_setting_for_lte#troubleshooting
- Please make sure that the SIM you are using is a confirmed LTE-M SIM from the link below.
The below link will direct you to an external website.
https://developer.sony.com/ja/develop/spresense/specifications/spresense-lte-sim-list