Only showing relative pages

I suspect you have been relying on a bug which I have since fixed. The plugin defaults to restricting a “page” listing to “sections” where a section is defined by the top-most page in a hierarchy, in your case “Page 1” because the A-Z listing is on a child page of “Page 1”.

The current solution, while not ideal, is to add a small bit of PHP code to your theme’s functions.php file, which replaces the sections to consider with an empty list. This causes the plugin to show all pages regardless of hierarchy. Take care to ensure that the code is within a <?php tag, which should be opened on the first line of the file:

add_filter( 'a-z-listing-sections', '__return_empty_array' );