HALO MCC Possible Microsoft Family Safety Issue

This may be a question for any parents on the forum. I have found references to the issue in other forums, but no one seems to have a solution for it yet, so thought I would try here.

I just purchased HALO MCC through Steam for my Son. It appeared to install on his Win10 PC with no issues, but after starting the game and clicking on the Sign in button, he gets the error message:
Microsoft
Something went wrong
Your parent has blocked access to games and apps that aren’t published by Microsoft. If you want to use this app, ask your parent to visit account.live.com/mk and go to Manage this child’s access to third-party apps for your account.

The link in the error message takes me to basically an empty page, that contains a further link to the Microsoft Family Safety site.There is no option to “manage … access to third-party apps”.

In MS Family Safety, I have checked that my Son’s account has Apps and games rated up to age “Any age” set. I have also checked in the App and game limits section to confirm that the App “halo: the master chief collection” is not blocked or have any time limits set. Lastly I tried uninstalling and reinstalling MCC.

If anyone has a solution to this problem, or even any ideas on any other things to try, I would be grateful to hear of them.

Thanks.