Old Player Account Issues
Well, I know for a fact that accounts are not banned ‘due to inactivity’. Perhaps, he read the message incorrectly. It is possible his account has been compromised. Any or all of your friends can contact Customer Support and will get help accessing their accounts. They can use the link at the top of this page, or any other GW2 page. ‘Support’.
That’s part of the problem, no one can figure out why they cant log into their accounts, the reasons are totally vague and they cant find out any way to solve the issue.
As I said, each of your friends needs to contact Customer Support so they can work on their individual issues.