Facebook tracks clicks on ads before the page loads. ScreenSquid tracks users after the entire page has loaded. If the user bounces before the page has loaded and ScreenSquid has a chance to start, the session is not recorded.

Fast bounces that prevent analytics from working properly are a common issue when using advertising networks as ads typically have a high bounce rate. You can read more about this specific issue on Facebook’s help desk here.

https://www.facebook.com/business/help/147965221941551