(Updated on 6th Jun 2020)
We just updated a new version for the target device where will be installed your child' device.
It fixed "Device NULL" bug - in case the parent have ever installed the app and removed the app from the target device, and after that, they do install again, they will see an error message: "Device is NULL or empty".
So, install this new version at https://android.thetruthspy.com again, and the bug will be fixed.
Let us know you meet this, and we will offer ten days more for free using.