Unable to load https://<URL of the hosted feature service>/FeatureServer/updateDefinition status:403

Error Message

When enabling editing for a hosted feature service published to Portal for ArcGIS, the following error is returned:

Error:   
Unable to load https://<URL of the hosted feature service>/FeatureServer/updateDefinition status:403

Cause

Portal for ArcGIS fails to access the public URL configured on the web adaptor.

Solution or Workaround

Set the WebContextURL property in the system properties of the portal. For more information, refer to Portal for ArcGIS: Configure your portal to use a reverse proxy server and browse to 'Set the WebContextURL property'.