[Loki[D.d.G]]

Firstly, are you wearing the Caretaker's Veil? If yes, the you should be able to activate the puzzles. But they can be pretty tricky to target, depending on what camera angle you are using. With the free cam i found them quite impossible to target. Try switching to the camera to the one where you are looking directly over your character's shoulder... that should make the pedestals easier to target... at least it did for me.