Common issues are:

* Sending the wrong message to a specific target group
* The product/service is too complicated or not appealing enough
* The reputation is not there - case studies, testimonials and actual reviews

More expensive products and services need a solid portfolio of existing customers and successful projects or stories. Marketing is not a one-shot thing and prospects often have to be warmed up for weeks or more in order to get comfortable and convert to users. That's where freebies, educational resources, free consulting and more come into play.