I have an image which I have duplicated several times onto a new canvas. I now want to use the Clone Stamp and other tools to retouch but they dont work. What do I have to do to get these tools to work on the new layers?

I don't recall if Photoshop CS had "sample all layers" for the clone tool. If not, just make a new blank layer and copy a merged version onto it (shift+ctrl+alt+E), then do your cloning there.

Thank you for that