The on-premise agent cannot reach the company's Sage database just now: it is waiting for the database server to answer, or it has stopped serving the company until the database or its sign-in is fixed. The request was refused at once. 503, retryable. Nothing was executed.
OPDC API error code
UPSTREAM_UNAVAILABLE
HTTP status 503
The API answers with a problem document (RFC 9457) whose type is https://twinn.engineering/errors/upstream-unavailable, and with X-Error-Code: UPSTREAM_UNAVAILABLE. Branch on the code, never on the detail text.