Hi Simon, I can imagine how frustrating that must be trying to set up your childs account on a new Windows 11 laptop and hitting a greyedout button feels like youre stuck before you even start.
If the Add someone button is greyed out in Windows 11 Family settings make sure you’re signed in as the family organizer confirm your Microsoft account is synced on the device repair or reset the Family Safety app install any pending Windows updates and if it still doesnt work create a local account for your child first and then link it to their Microsoft account.
When the Add someone button is greyed out are you signed in as the family organizer with your Microsoft account and is the device fully synced or is it still using a local account?
Best regards
Lucky Charm