I changed my nickname some time ago. In ticket system still my old nickname, so i can't make tickets, someone can change from DeadPoolHu3 to JavaBond please?
Sadly this is an issue (I know a few people with old usernames in the ticket system), but you should still be able to create tickets as it is done from in game by doing /ticket.
This is an open issue we are working on. As tonalom said you should be able to /ticket from in game or use the forums in the mean time. I assure you this is being looked in to.