Are you trying to edit online? Because they updated Twine recently, but the online editor isn't caught up to the new version (or wasn't, last time I checked.) When I tried to run files I've edited with the new version in the online editor, I remember it giving me the same error message. What's been working for me is downloading the Twine editor to my computer and editing the files there.
Your problem might be different though, if you could tell me more I could have a look.
And I might make a Twine game for this, we'll see. :)