A lot of beginners face the problem of picking out too many products to promote at the same time. It is hard to keep track. You want to focus on one or two to start off. Try to optimize them before assuming that the Clickbank product does not sell.
Another big problem is that just because one of the products tell you that you can earn huge commission does not mean that will get a lot of sales. Let's say it sells for $200 and gives you 75% commission, that sounds really good right? You have to know that not many people out there are willing to pay that much money to buy a digital product since that is all Clickbank sells.