I am unable to FaceTime my son any more

I can facetime my son iPad (via via icloud email )both audio and video without problem. (The ipad Air 2 is (M1) wifi version and connected to the home wifi all the times with screen time configured).

However after installed an parents control app called Finymy kids on my iPhone 14 pro max (ios 17.6) and pingo app on my son iPad (ios 17). The facetime from me don't work any more. I can only text message him. But my son can facetime me without any problem.

"My son iPad have choosen his icloud email for face time connected. "

1) I have tried to remove all the apps in both iPhone and iPad : restart both devices and also

2) upgrade both device to the latest iOS but still failed.

The iPhone prompt please choose other number or email for face (my son icloud email can't be used)

What wrong for my case and any solutions to this . I feel very frustrated as the trial app even make me worst then before.

thanks first

[Re-Titled by Moderator]