I might have missed something but the sequence should be:
After you finished the puzzle, go down to the catacomb and see that it is dark.
Look at an opening similar to the one upstairs where you inserted the object.
Go back upstairs and take the object from the wall.
Go back down and insert the object on the similar opening in the catacomb. Now there will be light.
If it is not answered above - post again, OK.