I have this same issue on a nest mini in the uk.
When I ask it to call someone it will start a google meet call with them, but the same doesn't happen for my child.
My child is managed by Family link.
You're not able to add them as home members, when I try in google home it says "Add to devices instead / You can't invite your child to join a home, but you can add them to smart displays and speakers with parental controls. / Cancel / Add to devices". I follow through and am able to add them to the nest mini.
In the family link App, for my child, in "Content Restrictions/Google Assistant/Parental Controls/Assistant Features/Calling", '...can make and answer calls' is selected.
In the Google Home app, in Household contacts, I am configured as a "household contact", with the nickname "dad", and the option "Anyone with access to your displays and speakers will be able to see and call dad. Calls will appear from the person who set up these devices" is selected.
Their voice match is set up, and when they ask the nest mini "what is my name", it knows who they are.
I have added myself to their contacts in their google account as "dad".
When he asks it "hey google, call dad", it says "Before you can make a call on Duo, you'll need to complete a step in the Google Home App. In the mobile app look for 'more settings' and select your device from the options, then follow the steps for Duo calling".
The curious thing is, that Duo doesn't exist any more.
