Thanks you all. It helped lots your posts to figure it out. It is working now for my Toddler in car seat

 

According to the manual, check if you have that symbol turned on:

If so, if there is no passenger on the rear seats, ventilation will only be on the front seats.

 

The far right button on the a/c contols turns the rear air off/on. The vent itself has a roller switch for air volume contol.

 

I feel like it's all backwards, light on, vents off.

That rear vent is nice for kids in the back. It won't blow then away, but sure keeps them more comfortable.