Error 133010 · HTTP 400

Sending number not registered

The code that looks like it is about the recipient and is about you.

Cause. Your own sending number has not completed registration on the Cloud API. Despite sitting in the same numeric range as the recipient errors, this one is about your account, not the person you are messaging.

Fix. Register the phone number with a POST to PHONE_NUMBER_ID/register. Treat it as an account-level alert: every send on the line fails identically until it is fixed. Do not suppress the recipients. We had this classified as a per-contact failure, which would have walked an entire audience into the suppression list one message at a time for a condition none of them caused.

Whose number is not registered

Yours. "Phone number not registered" means the sending number has not completed registration on the Cloud API, and the fix is a POST to PHONE_NUMBER_ID/register. It sits in the same numeric range as the recipient errors, which is a good way to get it wrong.

We got this wrong, and this is what it would have done

Our classifier had 133010 in the set of codes that suppress the contact. Because an unregistered sender fails every send identically, that would have walked an entire audience into the suppression list one message at a time, for a condition not one of those recipients caused.

It would also have been quiet. A suppressed contact still reads as opted in, so the consent screen shows nothing wrong while every message to them is dropped. We checked production before changing it: all 47 suppression rows were genuine keyword opt-outs, so the path never fired. It is now classified account-level, alongside 190.

Handling

Register the number, then resume. Treat it exactly like an expired token: one alert, no retries, and nothing recorded against the recipients.