Unable to view a hosted scene layer in Portal for ArcGIS

Description

When attempting to view a hosted scene layer in Portal for ArcGIS published from ArcGIS Pro, the layer does not load, and returns the following error message:

Error:   
<layerName> cannot be added
Scene service is missing root node.

Attempting to delete this layer in Portal for ArcGIS fails, returning the following error message:

Error:   
Some items were not deleted because they are delete protected or have dependent items.

Cause

The SceneCachingControllers geoprocessing service in ArcGIS Server Manager is not running. This prevents the creation of scene layer nodes in the CouchDB tile cache data store.

Solution or Workaround

1. Navigate to the ArcGIS Server Manager site, and log in as an administrator. The default path is:

https://machineName.domain.com/webadaptorName/manager

2. Navigate to Services > System.
3. Search for the SceneCachingControllers geoprocessing service.
4. Click the Start icon to start the geoprocessing service.

Hosted scene layers can now be viewed and/or deleted in Portal for ArcGIS.