Any tips to get sales for new listings?

Just for some background info: I’ve taken an inexpensive yet highly rated online course to understand the basics of Amazon FBA and one of the pros of Amazon FBA compared to other forms of ecommerce (to my understanding) is the benefit of being on Amazon.com and not having to focus as much on marketing since the website brings in heavy traffic already. However, through three separate listings I have created this year, I am seeing very little to no sales for each product. According to the online course, a good presentation, which includes the title, images, description, and bullet points, along with selling a product with competitors in relatively but not extremely high BSR’s will get you sales organically on the website. I have followed the course’s instructions on how to present the product to the best of my abilities and even gotten a handful of friends to buy the product but with very little to show for it.

So my question is both in a general sense and for those willing to help in direct messages, specifically in my case. What contributes to a lack of sales? Are there any specific methods to increase sales for a new listing you would give a beginner?

I’ve also posted this question on r/AmazonFBAOnlineRetail so for those looking for answers that post is linked here.