4002: Phone not available

Phone is offline or unreachable. The sender line on your account, or its messaging connection, is not currently available. The line can show as registered in your dashboard while its messaging connection is down. Arrives as an HTTP 500 on synchronous requests, and also asynchronously as a message.failed webhook when the unavailability is detected after the send was accepted. Async failures of this class were previously reported under the generic 4001.

• Check the status of the sender line in your dashboard — though the line can appear healthy while its messaging connection is unavailable.
• Retry the request after a short delay — the line may come back online automatically.
• If the line stays offline, subscribe to the phone_number.status_updated webhook — most, though not all, connectivity issues emit it when the line recovers, so retry after a delay regardless.

• Sending messages
• Debugging