Hi Davin,
Thanks for your response. Actually, I checked with them and it seems like it was an issue with the URL as the Map Viewer does not parse URLs properly when they include the following characters (#:?=).
The KML file is there now, but it includes point locations and paths, and no symbology or feature analysis can be applied to it. My challenge now is to extract the point features and convert them into a hosted feature layer that gets updated in almost real-time. Any suggestions on where to start?