There are some reasons make you cannot see the GPS data (no data on your user control panel):
1. The app does not work anymore
Maybe the app was removed from the target device (your child's device). For this reason, you can have a look at Troubleshooting session.
2. The device does not have an internet connection
This feature needs an internet connection, so at the time the app read GPS information (with a timer) maybe it does not have an internet connection?
3. Your predefined interval value
Maybe you adjust the interval value into 1 hour or 2 hours. It is 30 minutes for default and you can adjust it into 15 minutes or even 5 minutes but it will kill the battery of device down quickly.
4. The GPS location option was not turned on yet
Normally the app attempted to turn on this option (GPS location option) but sometimes it was failed to be turned on. Maybe you should try to turn on manually.
For more detail about how to turn on the Location option in the Android devices, click here.