There are many reasons the shutter might be not working.The simplest is that autofocus is on, but the camera is pointing at something it can’t focus on (a solid color wall, for example). This can often happen when you’re not looking through the viewfinder/checking on the camera.
Also, certain camera settings can prevent the Unleashed from focusing the camera, like setting your camera so it is required to focus with the AF-ON button instead of half-pressing the shutter button. Others can prevent the camera from releasing if it hasn’t focused before. This includes the AF-S/AF-C Release Priority setting.
Nikon also locks the shutter release when the SD card is full, or no card is inserted and you are connected via USB (even if you explicitly allow triggering without card in the camera menu).
If none of these are the case, please send us a screen recording of the app, or even a video where you can see the app and camera to firstname.lastname@example.org. Thank you in advance for all your efforts!