In this article, we will explain how to fix the icon disappearing issue. ( Icon show up as square )
1. Login to the Wordpress dashboard.
2. From the left-hand sidebar of the Dashboard, navigate to Ninja Popups >> settings
3. Open advanced settings
4. Disable "Font Awesome" and "Material Design for inputs"
Also, If you don't want to use Ninja Popup plugin, You can deactivate it from WordPress dashboard >> plugins >> Installed plugins
If you have any question please visit Pixflow help center