Can't Upload .kmz File

I'm trying to create a custom map. I created a polyline in ArcMap 10.7 and saved it as a .kmz file to my desktop. The file is 5.38 kb in size. When I select this file from my desktop, a green 'upload' bar moves from left to right, on the Upload Activity window ... again and again, after pressing the 'Next' button. How do I add my .kmz file?