Did you fight Wavebringer? If not, have you talked to Din Ho, who is near there, and done everything he's asked?
If you can get into the building, you might find somebody else there. You may need to fight and defeat him first.
If that building is empty, you'll probably have to start the instance over. Teleport out, go to the portal and hop on, enter, then leave, then hop on the portal again and enter. The quest should reset.