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Messaging Error Codes: What They Mean

When a text message is rejected by a mobile carrier, goHappy may display an error code in your Outbox to help explain why the message did not go through for an employee. These codes usually point to an issue with the destination number or a carrier-level delivery rejection.

The most common carrier error codes we see at goHappy are 40008 and 40012.

Error Code 40008: Undeliverable

What it means
The recipient’s carrier rejected the message for one of several possible reasons. In other words, goHappy sent the message to the carrier, but the carrier did not accept it for final delivery.

Common reasons this happens

  • The carrier flagged the message as not deliverable.

  • The recipient may have restrictions on their line.

  • The message content or sending setup may not meet carrier requirements.

What to check

  • Confirm the employee’s phone number is correct and active.

  • Review the message content for shortened links or content that could trigger carrier filtering.

  • Verify your approved messaging use case and registration details are current.

  • Try sending again only after confirming the number and content are valid.

Error Code 40012: Invalid Messaging Destination Number

What it means
The destination phone number was rejected by the carrier as invalid for messaging. Possible reasons include that the number is unowned, deactivated, or otherwise not able to receive messages.

Common reasons this happens

  • The number was entered incorrectly.

  • The number has been disconnected or is no longer in service.

  • The line cannot receive SMS messages.

What to check

  • Confirm the employee’s mobile number is entered correctly.

  • Check whether the number is still active with the carrier.

  • Ask the employee to verify they can receive standard text messages on that device.

  • Update the employee record and resend once the number is corrected.

Best Practices for Troubleshooting

When these errors appear, start with the basics:

  1. Verify the phone number and if necessary update it in your HRIS/Payroll system so the updated number makes it to goHappy.

  2. Confirm the employee can receive SMS on that device.

  3. Have the employee text the word START to your goHappy number, found on the dashboard when you log in.