The Nold application doesn't open my gate.

Please make sure that your Nold Open device is wired and powered up correctly. On the hardware you should see a green LED light pulsating. Here you can check the installation guide: How do i install Nold Open?

You can also check the Bluetooth connection between your phone and the device. First enable Bluetooth in your phone's settings then open the Nold application. At this moment you should see a solid green LED light (stops pulsating).