I have installed the latest version of Joomla and SP PageBuilder 5.4.0. Even emptying the cache (joomla and browser) and the cookies in the browser didn't help.
The option "Popup Settings" - "Styles" - "Close Button" works.
But if you create a "Button" element and, as shown in the screenshot, call up the button's settings and set the link function "Action after Click" to "Close Popup", nothing happens when you click on this button.
You can now test here: https://kirchengemeinde-oker.de
The "Fenster schließen" button (element) on the bottom of the popup does not work.
The "Schließen" button (Popup settings) on the top is working fine.