HtmlAgilityPack download webpage which loaded asynchronously by javascript

Html Agility Pack is not mimicking the client side calls to dynamically load content into the DOM. It is a headless scraper that is downloading the static page given by the server; if you want that content, you will have to mimic the calls made by the client browser. If you do not want to try to emulate the calls a browser would make, instead of using a headless scraper, you can use something like Selenium to do this for you, the down side being, the browser will be opened on the host machine.