If your characters have not received their achievements since we added the achievement system, they will need to have their character manually checked. In order to update your achievements you can speak with the Chronicler of Deeds NPC. He can be found in Old Tarantia, Conarch Village and Khemi.
Please keep in mind, only achievements for non-repeatable content will be updated by the Chronicler. Repeatable content, such as dungeon/raid boss kills, will not be updated automatically and must be completed again for credit.