ERROR: 21612
Description
Message cannot be sent with the current combination of "To" and/or "From" parameters.
Possible Causes
Number formatting: The format you used for the "To" or "From" number may not be formatted using the E.164 format. ResQEngage standardises numbers using the E.164 format. If the "To" or "From" number of this message were altered by ResQEngage in a way that you didn't expect, try re-submitting the message with E.164 formatted addresses.
Destinations where ResQEngage does not have connectivity: It is possible that ResQEngage does not yet have service with the carrier you are trying to reach. Contact Support.
Sender ID restrictions in the destination country: Many countries limit which numbers, short-codes, and/or alphanumeric senders can be used in that region. Consult the SMS guidelines for the destination region.
Possible Solutions
Consult the linked documentation for each cause. You can also try sending again with a different "To" and "From" combination.