When your child download's an app you will be notified and asked to approve or deny the use of the app.
Until you respond to request for approval the app will not appear on the kid's phone. Its the same case if you have denied the app.
So for the app to appear please do one of the following:
1. Approve the downloaded app in the notification that you received.
2. Go to app management (Click child profile pic>App management and toggle the app that can currently not be seen on the child screen to on.
If you do not wish for the child to have access to the app: Leave as is.