If the above does not help, the problem is most probably in the map that we use for routing. The roads may not be tagged to be accessible.
The good thing is that you can do something about that yourself. We use OpenStreetMap, the free and editable map of the world:
Find the location on the map and click the "Edit" button. Select the road and check the properties. You'll need to tag the roads with "access=yes" or to make them accessible:
Normally we update our maps from the source every month. If you have edited the map, let us know via email firstname.lastname@example.org and we'll trigger the update. That may take a few days to process.