I am using the AddData Widget on a Developer Edition WAB application. It sits on our own servers but was created using our organizational AGOL account. It will be used externally by others who are not part of our organization (the general public). I have the AddData Widget configured to NOT include "My Content" and "My Organization" but to include ArcGIS Online. But when the user tries to add content from arcgis online such as "https://elevation.arcgis.com/arcgis/rest/services/WorldElevation/Terrain" this fails. All others fail too. I thought much of this content from AGOL should be available to the public through arcgis.com without a login. Is this not the case? Also, an AGOL login dialog does not pop up in any case.
Is there some setting I have missed? Thanks for your help!