CMS error 512 usually means that the modem encountered a communication error with the mobile network and could not send the message.
- 1. Check that your SIM card is working correctly: take it out of the modem, place it in a mobile phone and try to send an SMS, to make sure that there is no problem due to the SIM card (example: subscription expired).
- 2. Check the GSM signal, it must be sufficiently stable: go to Configuration -> Communication -> Monitor. The signal is indicated after the CSQ =. For a reliable installation, the signal must be greater than 10. If this is not the case, the modem must be moved to an area with a better signal or the GSM modem antenna must be moved with an extension cable.
- 3. In ALERT check that the modem is configured with the correct network operator of the SIM card (as below)