This means that route calculation and active route navigation is only possible if the underlying map has been downloaded to the Navigator in advance.
To download a map, select "Settings > Navigation > Map download" on your Navigator and click on "Select and download maps". There you select the desired region and download the maps.
Note:
Make sure you have an Internet connection at this time, as the map data is often several GB in size. You can often select only individual regions or the entire country for download.
The map data for the countries Japan and Korea is a special case – to use these maps, other map data must be temporarily deactivated.