Need more information. What exacly does it do? What light color are you getting? If you place your joysticks like this (\) (/) does it turn on the motors?
What exactly are you doing?
When you tap the start-button upper left comes a popup in the middle of the screen. Then you should slide the start-slider. Did you do this?
When you tap besides the joystick circles (on in), does the circles jump to your finger?
If not, check your phone.