Issue I found (and others too) with the achievements "Sharp-Eyed" and "Mastermind": for unknown reason the game may stop counting HO scenes/minigames, even after starting a new game after finishing. The solution that worked for me is: delete your current profile and create a new one. This will erase the broken counter. Start a new game and be sure not to use hints and your achievement will eventually show up.
My personal guess: the unknown reason might be exiting the game before finishing, so you best play it in a single session.