This happens in two cases:
-
Existing resource: a resource with the same external reference, or a
contact with the same email, already exists. When present,
invalid-params[].conflicts_withholds its ID. Use that resource instead of creating another. -
Idempotency-Key in use: an earlier request with the same
Idempotency-Keyis still being processed. Wait briefly, then retry with the same key. If it persists, check whether the operation took effect before sending it with a new key, or it may run twice.