Map Maker not finding locations (polygon method)

I'm creating a map that is based entirely upon cities, ruins, castles and monuments generally dating to the 17th Century and earlier.

I'm using the polygonal method so that the chosen locations are random. However, I'm having issues with some areas not finding any locations to show. For example, I chose the Alt-Berlin neighborhood of Berlin, which has streetview available, but the Map Maker says that no locations were found. Whereas the same amount of area in other cities found 50-100 locations.

Am I doing something wrong?