You would need to contact support so that can investigate. Take a look at the flight profile in virtual radar, especially the climbs and descents, which might give a clue. Also perhaps you've set specific power settings per leg, so changing the initial/overall power setting has no effect.

When I change power setting in Flight Details the flight time does not change. I have 6 different power settings in the plane profile. How is this possible? The endurance does change.