I have a similar question - I finished the game - without giving away too much I am quite sure the game ended but the last puzzle isnt colored in or whatever like the others are once you complete them. Does that means something else has to be done? I guess this is an ok place to post this question.
I have read other posts about this. Apparently, there is something that you do have to do still -- or something that you have to do differently. Keep searching, there were a lot of posts talking about this problem a day or two ago. I'm not near there, so I didn't pay too much attention to them. Good luck!