If there is a high elevation in front of the ball, a 3w may not clear it and therefore not travel very far.
Maybe if you can specify the course, hole and position in fairway, someone might be able to give you a reason.
Also did the display specify ball in fairway or was it just visual that the ball was in the fairway. Sometimes the display will show the ball in the fairway, but it really is not in the fairway.