Please make sure that you've completed the following steps in the "Schedule a Call" screen:
1) Select a Child who will be answering the call. Important: If you don't see a name below "FOR CHILD", then there is no child selected. In the "Select child" screen, be sure to tap the name of the child to select it. Pressing the back button in the top left will not select it.
2) Select a Reason for the call. Here also, be sure there is a reason selected.
3) Select when the call should start
4) As you can see in the screenshot below, there is a green round button in the bottom right, which must be pressed for the call to be scheduled.
After pressing that button, you'll see a timer counting down. Please make sure that you leave the app open during the countdown. Do not lock your device, do not press the "Home" button of your device, and don't open any other app.
Note: It's normal for the countdown timer to disappear after several seconds - the screen goes to black on purpose, so that if you want, you can put the phone near your child while the countdown is running. Tapping on the screen will show the timer again for several seconds.