unsupported_media_type

The request body has an unsupported content type.

HTTP 415. Nothing reached the broker.

Likely cause: Not application/json.

What to do: Send JSON with Content-Type: application/json.

Retry: No. The same request gets the same answer; change something first.

Listed under Requests and validation in Errors. Send the error’s requestId to support and we can find the request.