Hi, I am being asked to enter the activation key for a second time on the Mobile Zone and when I do this it says an error has occurred. I can see my sons phone on the Family Zone Portal but can't get past Activation Key request on the Mobile Zone?
I would recommend you to perform a clean uninstall before reactivating Mobile Zone on the device.
Since your son is using iPhone, you would need to remove MDM profile first through the IOS Settings menu:
Once you have removed the profile:
Let me know if this works for you.