The data appearing does not necessarily mean there isn't a network issue. Tableau has many high level maps local. You can test by zooming in on that server view to a lower level.
Check this KB for more help: Maps Do Not Display or Render Incompletely on Tableau Server | Tableau Software
I have experienced this issue several times and it has always gone back to network and Tableau Server administration. The correct ports have to be open on the network firewall of the maps will not render after publishing.