1.Sensor doesn't work

Open the cover, at the same time to check the LED light if blink red and green.
When open the cover, the light have not blink that means the dispenser have
not power on. Need to closed the cover well.You can hear “pa” when the
cover is closed well. Now the dispenser can work normally. The dispenser
powered on when you open the cover, the LED light will brink red and green
like this.

2.Power on, but dispenser doesn't work

Check the distance. The sensor distance for the dispenser is 0-12cm.
If the distance less than 12 cm, that the dispenser will sensor by itself
and keep in inductive state. So make sure the distance from the dispenser
sensor to installation plane is more than 13 cm.  Then it can work again.