Not slaying you did or did not follow the proper directions for flat towing but the manual warns of at 35 mph and a 50 mile limit, if not done correctly. From The manual:
"Vehicles with an Automatic Transmission - with Ignition Switch
Note: There must be battery power to properly move the transmission’s internal components to neutral in step 3. Also, moving the gearshift to the neutral position without first turning the ignition to the on II position limits the towing capability to 35 mph (56 km/h) and 50 miles (80 kilometers).
Release the parking brake.
Switch the ignition to the on (II) position.
Press the brake pedal, then move the gearshift to the neutral position.
Wait for a message indicating that the transmission is ready in the information and entertainment display, then switch the ignition off and release the brake pedal.
Disconnect the negative (black) cable from the battery. The anti-theft system is disabled until the battery cable is reconnected. See Changing the 12V Battery.
Note: The maximum towing speed is 70 mph (113 km/h).
Note: There is no limit on towing distance."