GC Data Action 403 Forbidden on ServiceNow MID Server

Looking for advice on why the Genesys Cloud Data Action returns a 403 Forbidden error when posting to the ServiceNow MID Server endpoint for compliance logging. The payload validates in Postman but fails via the GC execution environment.

endpoint: https://mid-server.service-now.com/api/now/table/incident
method: POST
headers:
 Authorization: Basic {{encoded_credentials}}
 Content-Type: application/json
body:
 short_description: Compliance Audit Log
 priority: 1

The MID server logs show the request arrives but is rejected before processing. Is this a known issue with the BYOC gateway or a ServiceNow ACL mismatch?