I was trying to complete the achievement "City Knights" in City Core, however, when I try to complete the puzzle I am not able to click on the large chess piece, and the little help box thing says "you need the knowledge of A knights Tour to move the knight" I have the book, I have read the book. I have sent in a ticket and done a bug report, now I am creating a forum post because a friend is experiencing the same issue, I hoping I am not wasting my time again. I think I have attached a screenshot of my complete puzzle and not being able to click on the large knight piece. Does any one have any ideas what else I can do or try?

City knights-2017-03-01_134232.jpg