Hmm... it's hard to say exactly from the screenshot. What happens when you view it in Tableau Desktop?
If you can open it in desktop, check the map options (accessible from the menu) to see what map it is using. It is possible that the Tableau Server doesn't have an internet connection to the map provider. In that case, the map options can be set to use offline maps, but they are not available at certain zoom levels.
There were a lot of changes to the way the internet connection for maps worked from 8.0 to 8.1 and several problems that were fixed in the first few maintenance releases. Make sure you have a recent 8.1 version installed (or upgrade to 8.2!).