extra_ecclesiamB

Very hard to know what’s going on without more info.

With just this information alone, I would check that a static IP hasn’t been assigned to your son’s machine on your router and on the machine itself. If it has been assigned but another device was allocated that IP already, you will get an issue like this (though, usually, the problematic machine will still report a 169.X.X.X IP).

That’s the best guess without more info, though