Reporting API 403: Zendesk CSAT to Genesys Cloud Survey Mapping

Stuck on mapping Zendesk CSAT scores to Genesys Cloud surveys via the Reporting API. The endpoint POST /api/v2/analytics/reporting/query returns a 403 Forbidden error when trying to filter by the custom attribute zendesk_csat_score. This attribute exists in the Architect flow, but the API rejects the query. Running Genesys Cloud Public (EU-West) with Python SDK 10.5.0.

{
 "query": {
 "predicates": [
 {
 "type": "customAttribute",
 "attributeName": "zendesk_csat_score",
 "operator": "equal",
 "value": "5"
 }
 ]
 }
}