Guild Wars 2

Just as the title says… I am standing in front of treasure box with both key parts in inventory and it just won’t open nor give me achievment for completing the puzzle.
I am currently on Ruins of surmia, Arborstone, Blacktide match up…

P.S. kinda lame to make achievment in season one which ends in few days and it doesn’t work..

combine the key pieces?

I don’t know if any of this applies to you, but…

You need the key parts to unlock the door and chest. While a person with both key parts can open the door for players without, each player requires both key parts to open the chest for themselves.

If someone opens the vault for you, you can open the chest, but you will not receive the achievement for having done the jump puzzle, and if you do the jump puzzle before the chest resets; i.e. right away. You will be unable to complete the achievement until the chest resets for you.