Hopefully this might be of help - I had noticed several flights of late which didn't show routing on the map even though the route was in the database. They were all flights where I had entered the route in the database.
They weren't flights which came off the network into my RB range. I tried everything - re-entering the flight number, deleting the record and re-etering the data but the same result each time - no route.
Finally this morning I figured it out - If the numeric part of the flight number commences with a zero the program trims the zero before looking for the flight number in the database. For example XLA030 or XLA031 were in the database but the on screen flight showed no routing.
The problem was solved when I changed the database entry to read XLA30 and XLA31 :)