Thank you for sharing this question! The sales usually happen when the ads first run because Facebook knows who the most likely buyers are and once the ads have shown once, you are likely reaching the same people over and over.

The ad campaigns I have found that make the best sales are in the format of a post on a page with a lot of social proof. If your ads do not have social proof, then only the early adopters will buy. If your ads have thousands of likes, shares, and comments from a post on your page, then you can count on mainstream sales.

If you want to chat more about Facebook ads, you are welcome to schedule a call!