4008: Tier quota exceeded.
The 24-hour new-conversation quota is exhausted.
HTTP status: 422 or 429, depending on the request.
The channel limits how many distinct customers a new conversation may be started with in a moving 24-hour period, and this template send would exceed it. With a known retry instant the response is 429 with Retry-After and error.retry_after (a minimum wait); without one it is 422. Nothing was journaled.
Troubleshooting
Section titled “Troubleshooting”- Wait at least error.retry_after seconds when present; replies inside an open customer window are not counted.