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Mass Notification System (MNS) Error Glossary

This article explains the meaning of common response codes found in Voice and SMS alert delivery reports.

📱 SMS Message Errors

Response Description
Message cannot be sent with the current 'To'/'From' The sender ID or number type (e.g., shortcode) is not allowed for that number.
Shortcode not supported by carrier The recipient’s carrier does not support receiving messages from shortcodes.
Destination device may be a landline SMS was sent to a landline that cannot accept text messages.
Device switched off / unavailable The device was off, out of service, or unreachable.
Number is no longer active The number has been disconnected or is no longer in use.
Destination number unknown The number is invalid or not recognized by the carrier.
Unknown error: 30008 / 30500 Catch-all error when the carrier provides no specific reason for failure.
Pending Carrier Result Message was sent but no final status was received from the carrier.
Blocked number The number has opted out or was blocked by the system or carrier.
Carrier unreachable / shortcode unsupported The destination carrier cannot receive messages from this sender.
Invalid number Disconnected, incorrectly formatted, or inactive number.
TLS/SSL connection error Secure connection to the messaging platform failed. Backend issue.

 

☎️ Voice Call Errors

Response Description
Declined / Rejected The call was actively declined by the recipient or blocked by the carrier.
User Busy The recipient was already on a call or had "Do Not Disturb" enabled.
Temporarily Unavailable / Service Unavailable The call could not be completed; recipient’s device or carrier was unreachable.
Destination number is invalid Number is not assigned, no longer active, or malformed.

Number not found / Does not exist

Number is unassigned or no longer exists with any carrier.
TimedOut Call attempt timed out without a response.
No Answer The phone rang but was not answered.
Call Failed / Hangup The call was dropped or terminated before completion.
Circuit Congestion / Network Busy Carrier network was overloaded and could not complete the call.
Hangup at: X secs The call connected and ended after X seconds (often due to voicemail or user disconnect).
Full message delivered The full audio message was successfully played.
Originator Cancel The call was cancelled by the system before it connected.
CPS Limit reached P The system hit a call-per-second (CPS) limit. Some calls may be delayed.
Invalid Number The number is disconnected, misformated, or inactive. May also appear as “Unknown,” “Not Found,” or similar.