Unfortunately, when meeting this achievement's requirement, the achievement fails to unlock.  Have tried two different computers.  From my research, I have tried all sorts of approaches:

Toggled Experimental Gameplay.

Tried opening the treasure chest with treasure map in main hand/offhand.

Deleted game and installed again.  Reset app's setting.  Deleted related temporary files.

Among many other trivial approaches.

Would appreciate any insight on what I could try next.  Thanks!  

EDIT:  My friend tried for this achievement as well and wouldn't unlock for him either.  This was on his own PC too.