`rail_not_available`

HTTP 400invalid_request

That plan cannot be paid that way.

Handling it

Fix the request and send it again. message says what is wrong, and param names the parameter where there is one. Keep the request_id: it lets Parasend find the request.

The error, as the API returns it

{
  "error": {
    "type": "invalid_request",
    "code": "rail_not_available",
    "message": "That plan cannot be paid that way.",
    "param": null,
    "request_id": "req_5e69684dc3de68bf8651a712"
  }
}