I have my starting page with unbounce (doing an A/B test) and also the thank you for buying page with unbounce. Also I have added the unbounce external tracking script to track conversions. Between my starting page and the thank you page there is the external payment page.

When I look now in unbounce I see conversions, so at the first glace it seems everything is working correctly. But as I see also the number of sales through my payment provider, I realized that unbounce is not tracking all conversions. I had 11 sales (payments coming in), but unbounce just shows me 8 conversions.

So my question is if I have done something wrong in the set up? Or if by nature of the tracking code, it can be that not all conversions are tracked - e.g. for people that do not allow cockies?