Hi,
Thanks for explaining the issue so clearly. It sounds like the child’s new computer is signed in with their Microsoft account, but it hasn’t properly connected to your Microsoft Family group, which is why activity reporting isn’t working.
To fix this, first check that the child’s account is still part of your family group by visiting https://www.microsoft.com/en/microsoft-365/family-safety?ocid=family_signin.
If it’s missing, you’ll need to re-invite them using their email. On the new computer, make sure they’re signed in with the same account that’s linked to your family group. You can confirm this in Settings > Accounts > Email & accounts.
It also helps to install the Microsoft Family Safety app from the Microsoft Store on the child’s device and sign in with their account. This can help sync the device properly. Then, visit account.microsoft.com/devices to see if the new computer shows up under their account. If it doesn’t, try restarting the device or signing out and back in.
Once the device is recognized, go back to your Family page and check the child’s profile to make sure Activity Reporting is turned on. You might also want to enable Web and Search History and App and Game Limits.
If things still aren’t working, removing and re-adding the child to your family group can refresh the connection. Also, make sure the new computer is fully updated through Windows Update, and try signing out and back in under Settings > Accounts > Your Info.
Let me know how it goes, happy to help!
Regards,
Edward