This video shows how to remove the detachable hitch receiver on a Land Rover LR3, Range Rover Sport and LR4. We primarily use our tow receiver to hold our KUAT NV Bike Rack: http://amzn.to/2wjf5Bh
The locking pin on the quick release hitch receiver must be retracted in order to attach it to the vehicle. You will need the key in order to turn the knob completely to fully retract the locking pin. If you have having trouble fully turning the knob, they key may be moving slightly so make sure the key is fully turned when you turn the knob.