The child-proof locks are enabled. Inside the rear doors is a white switch/lever. Flip it to the "off" position.
Try settings -> vehicle settings -> doors
There are several ways you can set the locking/unlocking behavior you prefer.
I set mine to be gear-triggering. i.e. lock when shift out of P, unlock when shift into P.
You can go by speed (~5mph) to lock, but you have to unlock yourself.
There is a walk-away lock if you have the smartKey access.