VENDOR_NOT_CONFIGURED
HTTP 503No
No usable vendor key/credential configured for this capability — a CONFIG gap, not a transient outage (retrying won't help; hydrate a key or finish vendor setup). Distinct from VENDOR_DOWN.
By default a failed call returns a result with an error instead of throwing, so your business flow is never interrupted.
Published error codes are permanent: their meaning never silently changes, and deprecated codes keep returning for at least 12 months.