HTTP status codes / 4xx — Client errors
Reserved for payment; used in practice for quota and billing walls.
Officially "reserved for future use", but real APIs (Stripe, cloud providers, paid tiers) use it for billing problems: exhausted credits, expired subscription, payment failure.
Check your plan/quota in the provider dashboard; the response body normally names the billing issue.
Server-side note: The response body normally names the billing issue; check the provider dashboard.
The fastest way to pin down a 402 is to reproduce the exact request and inspect what actually went over the wire — status, headers, timing and body, without your app code in the way. That is what an API client is for; ReqPad does it from your phone, with every request saved to history.
400 Bad Request · 401 Unauthorized · 403 Forbidden · 404 Not Found · 405 Method Not Allowed · 406 Not Acceptable — or the full reference.
Build the request, send it, read status + headers + timing — on your iPhone. Free to start.