Motor shield V2

Hi ,
i bought this shield and i am very happy of it but i have a little problem.
When i try to connect two dc motors just led B indicator is on otherwise the A indicator is off ; so when i try to load a program just one motor rotate the otherone is off.
I do something wrong?
I use a 9v battery for power motors.

Thanks for your answer.

Hi, can you upload your code?