Last week I encountered a confusing behaviour of MFN. I started a tour with about 20 waypoints, the route was calculated and I followed the instructions. After a while (maybe 10 minutes) MFN told me "recalculating the route” and then "route not found” and stopped navigation. In "route info” – "itinerary” there were "no manoeuvres”.
It took me some time to realize it must have to do with HD traffic. HD traffic info is not present directly after application start, it only appears after a certain time. So these informations are not present if driving begins immediately after starting the app.
I had to deselect one waypoint after the other until I found out that two of the waypoints were on a temporary blocked road. Only then I could change the route.
This approach is rather impractical, at least I would expect that MFN explains which waypoint causes the route not found-message in the form of "waypoint 5 closed” or whatever.
I tried it a few times today: Opening MFN without any further action HD Traffic only displays the message "No Traffic information available. Waiting for data from the HD Traffic server...". I stopped waiting after 15 minutes. Only when I start navigation it takes not more than 10 to 15 seconds and traffic information is available. Maybe in my case mentioned above I actually did not have an internet connection at the beginning of the ride.
But that's not the point. The point is that a "route not found"-message without any information why the route is not found is not very helpful, especially in the rather simple case when a waypoint lies on a blocked road.
By the way: The same messages ("route not found", "no manoeuvres") appear when a waypoint is on a toll road and using toll roads is disabled. In this case a message like "one waypoint lies on a toll road" or something like that would be very helpful.