I've just added an edit to the above post to show that I found the problem.If you are having a plugin conflict you could also cheese it and have a ring around the puzzle (using VS event on regionid) that changes the player to through and a ring right outside of that that turns through off.
Thank you for replying so quickly and putting me on the right track. It was a great tutorial and it makes sense that you would do it without plugins installed. Now that I (kind of!) understand how it all works I'm going to see what sort of things I can apply it to. Trying to figure out what was wrong made me really study the script to try to understand it and some of it has made its way into my wee brain, so all in all, a good learning experience. Thanks again.