I am unable to put the 3rd key into the wall puzzle to be able to openthe secret room. i have them in the inventory but there are only 2 showing on the wall.

when i try transferring the keyout of the bag nothing happens. what have I missed? cheers Alfoil

Are you talking about the oars-paddles as the keys?
If so, the slots to place them on are small and has to be clicked exactly.
The 2 side oars have top and bottom holes. The center oar can use the side holes as well as the central one.