mobile_step_up_callback_refused
The mobile step-up return address is not registered. Return to the app and start the confirmation again.
Problem shape
Every non-2xx response is an RFC 9457 application/problem+json body. The type URI below is stable and machine-matchable, so branch on the final path segment (the code) and treat the status as redundant confirmation. See the error-handling guide.
{
"type": "https://docs.vocapable.com/errors/mobile_step_up_callback_refused",
"title": "…",
"status": 400,
"detail": "…",
"instance": "/v1/…"
}