Well, you have an errrant "true;" in your code, so there's probably a syntax error. I hope you're looking at your browser's console/developer tools to see such things.
The correct code is demoed
here. The onSuccess is called as expected. However since that page doesn't have your GTM code, it fails (understandably) on the line that calls _gaq.push().
If you post the actual URL of your page I could take another look.