How to Set Up a Custom Conversion for your Facebook Ads

To do this you need to have control over your thank you pages for either a lead or a sale because your pixel needs to be on this page.  

For example, if you take people to Paypal to pay then you don't have a thank you page you can track because people leave your website.  Or if you use a system for your landing pages like Lead Pages make sure your pixel is on your thank you page in that platform.  Just because you have it on your website does not mean it will be on your thank you page if you use another platform.