Is your Tableau Server configured to use the proxy to connect to google maps?
The main reason can be if your Tableau Server is not able to connect to google maps (via internet) it will not load the map correctly or will not show the map.
I can connect to google maps, when I log on with my user. But if I tell someone else to log on from their iPad using the same account, they cannot connect to Google maps. Once they make an action they just get a black screen.