Facebook
pixel track the data from user browser side that is not working
properly now by the recent update of IOS 14/14.5 also others browser
Firefox, Safari, Chrome, Yandex etc. Intelligent Tracking Prevention
(ITP) algorithms. Due to the update, Facebook conversion API is best solution for collecting user data with protection from website. So you need to capture your data through Conversion API or Server Side Tracking instead of browser. Then utilize user data for advertising.