I've created a georeferenced image overlay in Google Earth, saved it as a KMZ, and uploaded to my ArcGIS account. When imported into Map Viewer, the overlay looks good: https://www.arcgis.com/sharing/rest/content/items/dce38dd3af6f4d6c86ec8d6eda2cd2a0/data
However, when I try to used this map as a Basemap for a Storymaps Guided Tour, the layer holding the KML data doesn't appear: Cemetery (Draft Cemetery-Focus) - ArcGIS StoryMaps
I've gotten KMZ overlays to display in other Storymap Basemaps using this same method, and I'm confused why its not working with this Map.