Do you happen to have the URL of the thank_you page the code is supposed to be firing on as well? If you are able to do a test purchase and copy that URL I can check that as well. It will look something like:
If you don't feel comfortable posting in on the forum you can email me at noah@42connect.
I'd also suggest using this Google Tag Assistant plugin if you're not already to see which tags are firing on which pages. There seem to be some interesting things going on with some of the Google Analytics tags on the site as well.