Since version 3.3, Astra theme default font icons have been replaced by SVG icons. When SVG support is enabled, the astra.woff file and the icons mentioned in this document are not loaded anymore. You can find out more information details in this article.
If you still wish to use these icons, you need to disable the SVG support.
Astra comes with a custom lightweight & beautiful icon font. All icons used in the theme are shown in this library.
You can find each of the font-icons available with Astra and its CSS class described below-
Here is a screenshot that shows how the default added icon appears.