Errors and retries

Status	Meaning	Action
400	Invalid request	Correct the request before retrying.
401	Invalid or missing API key	Replace the key from secure server configuration.
403	Merchant is not eligible	Complete onboarding or contact support.
404	Resource not found	Check the ID belongs to the current merchant.
409	Conflicting state	Check passed data and ensure it's correctness.
429	Rate limited	Retry with exponential backoff.
5xx	Temporary service issue	Retry safely with an idempotency key.