Your app is running in the background. To get the baby monitor image back to the foreground there are a number of options you can choose from:
If it is visible on your screen, tap the red bar at the top of the screen and your ugrow app will come back to the foreground.
Open the app again by tapping the ugrow app in your phone's menu.
If you receive a notification then you can also tap that and your app will reopen.
It is also possible that the bandwidth of your internet connection is too small for streaming video. Please check the DFU chapter "Video and audio quality optimization" for more information.