The environment is AutoCAD 2018, using the ArcGIS for AutoCAD plugin, version 370. In the main, it works fine, but when trying to access http://gis.maricopa.gov/arcgis/services > Imagery > AerialComposite, the system just hangs and finally errors out with the message "Error adding service. The remote server returned an error (403) Forbidden." The problem is that this same fully-formed URL (http://gis.maricopa.gov/arcgis/rest/services/Imagery/AerialComposite/MapServer) works fine in ArcMap, ArcGIS Earth and open source QGIS. Can anyone tell me what might be going wrong for this particular service? All of the other http://gis.maricopa.gov/arcgis/services endpoints work fine-- except for any of the imagery layers.