Possible reasons for intermittently "Modem Error (Unknown error)" include the following:
- SIM card usage could have exceeded message quota set by your Telco provided. Try plugging in the SIM card into a phone and see if you can send out a SMS to check if this is the case.
- Temporary loss of signal coverage network. You may need to repositioned your CG-ONE unit or purchase a long antenna from us.
- If using a prepaid SIM card, it could have run out of prepaid balance.