Geocode service published in ArcGIS Server 10.6.1 returns no results, when it uses a locator created from Create Locator Geoprocessing tool in ArcGIS Pro with a role type to Street Address.
This issue occurs because the locator was built without administrative zones such as city and state. Options for ArcGIS Server 10.6.1 are the following:
1. Create the locator with zones and include at least 1 zone when searching
2. Pass in a location for each request if using the REST API. Most client applications such as ArcGIS Pro and ArcMap already do this when the user is zoomed in on the map.
If neither option works, upgrade to ArcGIS Server 10.7 or newer server.