I've looked through the little help documentation on ArcGIS Earth I was able to find online, and I'm not seeing how to resolve this error in there. I'm connecting to ArcGIS Earth through our Portal site (which is version 10.5.1), rather than through ArcGIS Online. I've noticed when I go to add a basemap or terrain within the ArcGIS Earth application, I'm only shown custom-curated content, not the ArcGIS Online-hosted basemap content that I'm used to seeing in ArcMap, ArcGIS Pro and Portal for ArcGIS. Why is this? Is there something I'm missing? Where are the topography, imagery, etc basemaps I normally have access to?