Try going to the tribalwars.net site again and logging back in. If you still get that message, try using another browser. If using another browser works, then go back to your original browser and clear browsing history (or at least empty cache).
If none of that works (some of it might not even help, I'm liable to be wrong :icon_redface
, try to submit a ticket through the main tribalwars.net page
.