Hi,
I have a very simple kml file exported from Google Earth with one polygon.
When I import it to ArcGIS online (e.g. by "New Item" in Content, or adding as a layer to a web map), it finishes with no errors, but the resulting layer is empty.
When I convert the same file to geojson (e.g. using mygeodata.cloud's converter), then import the geojson file, it works properly and I see the polygon.
I'm glad I have a workaround, but it's inconvenient to have to go through the conversion step. Am I doing something wrong?