Basically, I keep trying to cast 'Lumos' on the Devil's Snare, but it's not working. I'm on the Legilimancy bit, where you're at King Cross Station. I keep holding down the stylus to cast Lumos, and the circle appears on the top screen, but when I hover over the Devil's Snare, I can't cast it at it.
I've tried on different levels as well, but I can't cast any spells at the Devil's Snare.
Any help or answers most appreciated!