(PI3) GPIO pin stay high, even after set to low

Question

I'm trying to turn on and off relay using raspberry pi 3. But after successfully turn on, it will stay on even after I set GPIO pin to low.

I use pi4j example and python example, both of them give me same result.

this is the code

final GpioController gpio = GpioFactory.getInstance();

    final GpioPinDigitalOutput pin = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_29, "MyLED", PinState.HIGH);

    pin.setShutdownOptions(true, PinState.LOW);

    System.out.println("--> GPIO state should be: ON");
    Thread.sleep(5000);

    pin.low();
    System.out.println("--> GPIO state should be: OFF");
    Thread.sleep(5000);

    pin.toggle();
    System.out.println("--> GPIO state should be: ON");
    Thread.sleep(5000);

    pin.toggle();
    System.out.println("--> GPIO state should be: OFF");
    Thread.sleep(5000);

    pin.pulse(1000, true); // set second argument to 'true' use a blocking call

    gpio.shutdown();

Please help, thank you.