A report job id this API does not hold: never issued, another customer's, or past its retention. 404. Also the answer for the result of a cancelled job, which will never have one.
OPDC API error code
JOB_NOT_FOUND
HTTP status 404
The API answers with a problem document (RFC 9457) whose type is https://twinn.engineering/errors/job-not-found, and with X-Error-Code: JOB_NOT_FOUND. Branch on the code, never on the detail text.