If you see a black screen when viewing the map, it usually means that some art files haven't downloaded completely. Often, the game just needs a little more time to load these visuals. This can commonly occur if you've recently cleared your cache, reinstalled the app, or switched from offline mode.
If the display issues continue, please leave the game open for up to 10 minutes to ensure everything downloads fully to your device. The exact time needed may vary depending on the strength of your internet connection.