on line gaming

It's sad people tend to do this a lot People attempt too scam people. If your password on that account has changed and your kid can no longer sign in he needs too recover password soon as possible.

try removing the account from the console, doing a hard restart, hold the power button for 10 seconds while the system is on, and then re-adding the account

What happens when he tries to play?

Since Fortnite is quite popular, especially with kids, malicious people often try to take advantage of "gullible" kids and promise them V-Bucks, Skins or other stuff if the kid gives them access to their account.

Usually, Microsoft Accounts are very safe against hacking. However, if the kid used a weak password, did not use Two Step Verification, or even voluntarily gave a stranger access to his account, then the stranger could have abused your kid's account.

First, your kid should try to go to
https://account.live.com/Proofs/Manage and try to sign in.

If it's possible for your kid to sign in, they should immediately change their password.

Then the kid should check if the malicious person added their own email or phone numbers to your son's account as the person could then still use these added emails or phone numbers to re-gain control of your son's account. Remove any unknown emails and
phone numbers.

Then further down on the page is an option to enable Two Step Verification, and after enabling that function, to set up an authenticator app, if your son uses a smartphone.

With Two Step Verification, any person trying to sign into your son's account will be asked for an additional code, that is only displayed on your son's phone. Without the phone, no one can access your son's account, even if they somehow were able to steal
the password.

If the kid has regained control of their account, they should check under
https://commerce.microsoft.com if their games are still listed there.

Also, since a Mod had to remove the email: Be careful about revealing personal information like emails in a public internet forum.

Educate your kid to NEVER tell anyone their account credentials. Especially not persons that promise them free stuff in games.

These are all malicious tricks to gain access to other peoples account, and then hope they have a payment instrument on the account they can then abuse to buy stuff for themselves.

Yeah, the real problem is when you cant get this kind of information on internet, this a example for Overwatch, i found the image of the back of the Box, but usually you dont found in other games even in the site of the developer, they put only the picture
of the front of the box.