It would be Google Adwords. There is no tracking for "AdSendse" which is the advertising platform you can use to display ads.
I think what you mean is Adwords.
Since Adwords tracking tracks ppc (paid search) converison, it will only show a conversion if the click came directly from an ad you are running. So in order to test it, you need to first do a search on Google then find one of your Paid Search ads. Click it, then make a purchase on your site (so you came "through the ad" in order to get to the site).
This is the way Google works with teh paid search conversion (and they should as tracking a "conversion" for paid search traffic that did not come from an ad would be in accurate and wrong.)
Make sense?
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