1) Turn on the ACF shortcode if you have a new install of ACF and bypass the non-public post check. 2) If the shortcode doesn't work, use a Popup Maker filter to tack on the popup's ACF if it has one. I.e., use 1 or the other not both.

acf_shortcode_hooks.php

<?php // Ignore this first line when copying to your child theme's functions.php file.

/** Try using the ACF shortcode first. */

/** Turn on the ACF shortcode as of ACF 6.3.0. 
 * https://www.advancedcustomfields.com/resources/shortcode/#enabling */
add_action( 'acf/init', 'set_acf_settings' );
function set_acf_settings() {
    acf_update_setting( 'enable_shortcode', true );
}

/** Make the ACF fields available to non-public posts like popups as of ACF 6.3.4.  
 *  https://github.com/AdvancedCustomFields/acf/blob/693e8defb70e35270a4636579ad3c5dc64521bc3/includes/api/api-template.php#L1051*/
add_filter( 'acf/shortcode/prevent_access_to_fields_on_non_public_posts', '__return_false' );

display_acf_popup_filter.php

<?php // Ignore this first line when copying to your child theme's functions.php file.

/** If the ACF shortcode doesn't work, use this filter as a last resort. */

/** Use a Popup Maker filter to tack on the popup's ACF if it has one. */
add_filter( 'pum_popup_content', function( $id ) {
	$id = pum_get_popup_id(); // Get the popup ID.
	$post = get_post( $id ); // Get the popup post type.

	// Extract the original popup content.
	$the_content = apply_filters( 'the_content', $post->post_content ); 

	// Get the ACF value in the popup and sanitize it for XSS. 
	// - Change "test" to the name of your ACF.
	// - Add security and more checks for malicious hacks as you need.
	$acf_value = esc_html( get_post_meta( $id, 'test', true ) );
	
	// Format the presentation of the ACF value. If there isn't a value, show a message or alternate text.
	$new_content = '<strong>Popup ID</strong>: ' . 
		$id . 
		'. <strong>ACF</strong>: ' . 
		( $acf_value ? $acf_value : 'Whoops, no ACF value!' ); 
	
	// Return the original content plus the ACF content.
	return $the_content . $new_content;
} );

// You can add the PHP code snippet to your child theme's <code>functions.php</code> file or
// with a third-party plugin such as <a href='https://wordpress.org/plugins/my-custom-functions/'>My Custom Functions</a>

Allow Access to Value in Editor UI Setting

Must turn this on for the ACF shortcode.