What web browser are you using? That may be an issue too. I'm using Chrome and can see the map display. However, it is slow to display. It takes about 10 seconds before I can see it.
Your map is kind of big, 6MB. In the desktop world, it's not big, but in the web, it is. It's a 6MB download of data to the web browser (which takes 2-4 seconds itself), then the web browser has to draw all the shapefile data.
Did you use the generalize option when adding the shapefile to the map? That will help make the data a little smaller. Also, if you have ArcGIS Desktop, you can generalize the data yourself before you add it to the map. The smaller you can make the shapefile, the better your map will perform.
Thanks,
Mike