The walkthrough says "There are several possible solutions, but the game is looking for one specific solution." That may be your problem. You don't have the "specific" solution the game wants even though you've found "a" solution. The mandala puzzle you'll find later on has the same problem. You may find "a" solution, but not the "specific" solution the game will accept.
The
walkthrough gives this answer
"Answer: Left side of pyramid, top to bottom, is 1,11,8,6; Right side of pyramid, top to bottom, is 7,12,4,3; Bottom of pyramid, left to right, is 2,9,10,5.)"