Assuming there is nothing obviously wrong, the next thing we check is that the load rules are correct and that the tag is supposed to be firing. This is often the cause for this kind of live/qa site difference - a load rule being set to a specific live-site URL, for example.
Next it's a matter of looking in either the network tab of developer tools, or the sources tab (if you are using Chrome) to see if that particular tag is being loaded.
If you would like us to take a look, please feel free to send an email through to email@example.com with the details.
Connecting data systems since the 1980s.