Geocoder w/ ArcGIS Server - Error 403: Access to this resource is not allowed

I am attempting to add a Geocoder transformer to spatialize address data using a published geocoding service on ArcGIS Server. When running the address data to the transformer, it rejects every feature with “Code 403: Access to this resource is not allowed”. The REST URL and Portal credentials are all correct and I am able to get to the service in a browser, as well as access and use the Locator in ArcGIS Pro to geocode addresses. With that being said, I don’t know why access to the resource would be disabled in FME but nothing else. Any insight or suggestions would be appreciated, thank you!