Make sure the hatch is closed. Open and firmly re-close it to be sure. It might look closed, but move slightly with the car's motion. And don't ask for the logic behind this particular error message for this particular fault.
Update: when the car was in for service, I asked about it. They said at some point the battery voltage was too low and that caused the error message. I am not sure the dealers know more than owners. When the 30k service was due, I used local shop for $100 instead of the dealer for $ 400!! They should get real.
