Work is completed whenever the given 2 conditions are satisfied:
(i) a force acts on the body.
(ii) there’s a displacement of the body by the appliance of force in or opposite to the direction of force.
If the force direction is perpendicular to the displacement, the work performed is zero. When a satellite moves round the Earth, then the direction of force of gravity on the satellite is perpendicular to its displacement. Hence, the work done on the satellite by the planet is zero.