Unable to access shared ArcGIS Server services via the service URL in ArcGIS Online Map Viewer

Description

ArcGIS Enterprise allows the sharing of ArcGIS Server services by connecting ArcGIS Server Manager to the ArcGIS organization and referencing the service URL. In some cases, attempts to access a shared service via the service URL in ArcGIS Online Map Viewer fail, and return one of the following error messages:

Error:   
The layer, <LayerName>, cannot be added to the map.

Error:   
Unable to create map: Unable to load the base map layer

Cause

The service URL is configured using a Local Area Network IP address. This configuration only allows connections within the same on-premise network, and cannot be connected to externally.

Solution or Workaround

In ArcGIS Enterprise, configure the ArcGIS Enterprise portal with ArcGIS Web Adaptor. Refer to ArcGIS Enterprise: Configure ArcGIS Web Adaptor for more information. After configuring ArcGIS Web Adaptor, access the ArcGIS Enterprise services via the newly configured Web Adaptor service URL.