Due to an issue after the launch, we noticed that the "Treasure Hunter" achievement is not progressing as it should be for some players. After installing this update, when you open the game and reach the Main Menu, the achievement should be correctly updated on the Steam.
There are a total of 28 chests in the game. If you haven't deleted your game progress after opening all the chests, the achievement should unlock when you enter the game after the update.