EA account can only be linked to one xbox account in its lifetime.

 I think this is hwat happened to my sons account.  He played and completed everything on his xbox.  we no longer have the xbox and gained access to the microsoft account to get into it on his pc.  It states its unplayable.  spoke to ea who were not too helpful and just said they can't help.  Even though we showed then screenshots of his achievements.  One very sad boy who has lost a whole load of progress and money :-(