Can't add user "64thunder" to a team.

I can add everyone else even fake players but for some reason when I use the command /team join [team name] 64thunder it does not add him to the team. It shows the message "Added 64thunder to team..." but he does not show up in /team list [team name]. Even when i use @a to try and put everyone on the server onto a team everyone is added but him. I've tried deleting the user data for him but it still wont work. I dont know what to do.