I have created a polygon, ensured that it has a projection and I can see it in the preview pane on ArcToolbox. When I zip it and add it to AGOL I end up with Unable to import this shapefile. (The operation was attempted on an empty geometry.) as an error.
I have attempted to use the "Repair Geometry Tool" but that does not seem to have worked.
When I re-opened it in ArcMAP I can no longer see the shapefile or zoom to it. I also tried adding the "Geometric Network Editing" Toolbar to ArcMAP. All of the buttons on that toolbar are greyed out though.
I georeferenced a gif which showed the boundaries of Prussia in 1700. I also added a layer with the modern administrative boundaries of the countries of Europe to help with common boundaries from then until now. I created the shapefile in ArcToolbox and added it to the project and created the features in ArcMAP.
Maybe recreate the polygon file and as the coordinate system, chose import and use the modern day boundary file as the template for your coordinate system? Something must have gone wrong when you created the shapefile. I can't seem to find a fix for your current one.
I found a solution but if anyone would know why this worked, please let me know. I created a geodatabase and then a new feature class. Added to ArcMAP and created the features just like before. This time I exported it to a shapefile and then added it to AGOL. Seems to work fine.