This evening, my son's Microsoft account stopped working - xbox live, Windows 8.1 sign in, web sign in, etc. After some annoying detective work, I finally figured out that I had to sign in with my account and verify that his account was authorized. Why the sudden change? He's been using his child account with my approval for over a year. Do child accounts require re-verification after some set length of time? Or did his verification get canceled when I recently changed the password on my own MS account?