duplicate_post_get_original & duplicate_post_create_duplicate not working

• I've searched for any related issues and avoided creating a duplicate issue.

Please give us a description of what happened

I'm trying to make use of the functions duplicate_post_get_original & duplicate_post_create_duplicate without success with Yoast Duplicate Post Version 4.5 and Wordpress 6.1.1. The first does not create a duplicate/return the original post. The second seems not to be defined.

duplicate_post_get_original is neither duplicating a post nor returning the original post id. Calling duplicate_post_create_duplicate leads to a fatal/uncaught error: Call to undefined function duplicate_post_create_duplicate()

To Reproduce

Step-by-step reproduction instructions

I've created the folowwing simple test code as page template. Post ID 1 is the "Hello World" Blog Post

<?
  duplicate_post_clone_post_link("Link Text","Before","After",1);
?>
<br><br>
<?
  $original_post = duplicate_post_get_original(1);
  echo "Original post: '" . $original_post->ID . "'";
?>
<br><br>
<?
  $old_post = get_post(1);
  $new_post_id = duplicate_post_create_duplicate($old_post);
  echo "New post: '" . $new_post_id . "'";
?>

Expected results

1. A link should be created, to duplicate the blog post with ID 1
2. The blog post with ID one should be duplicated, but ID of old blog post (ID: 1) should be echoed
3. Another duplicate should be created. ID of created blog post (ID: 3) should be echoed.

Actual results

The actual output looks like the following.

Before
[Link Text](https://logistik.at-fire.de/wp-admin/admin.php?action=duplicate_post_new_draft&post=1&_wpnonce=63f8d20dd5)
After


Warning
: Attempt to read property "ID" on null in
/homepages/14/####/htdocs/####/wp-content/themes/asset-management/geraet-copy.php
on line
32

Original post: ''


Fatal error
: Uncaught Error: Call to undefined function duplicate_post_create_duplicate() in /homepages/14/####/htdocs/####/wp-content/themes/asset-management/geraet-copy.php:37 
Stack trace: 
#0 /homepages/14/####/htdocs/####/wp-includes/template-loader.php(106): include() 
#1 /homepages/14/####/htdocs/####/wp-blog-header.php(19): require_once('/homepages/14/d...') 
#2 /homepages/14/####/htdocs/####/index.php(17): require('/homepages/14/d...') 
#3 {main} thrown in /homepages/14/####/htdocs/####/wp-content/themes/asset-management/geraet-copy.php on line 37

• duplicate_post_clone_post_link creates the link correctly. On pressing, the blog post gets duplicated.
• duplicate_post_get_original obviously does not return anything / null
• duplicate_post_create_duplicate seems to be undefined.

• Which browser is affected (or browsers):

• Chrome
• Firefox
• Safari
• Other:

Used versions

• PHP version: 8.0
• WordPress version: 6.1.1
• WordPress Theme: Own
• Yoast Duplicate Post version: 4.1

Start by inspecting the public definitions and usages of duplicate_post_get_original, duplicate_post_create_duplicate, and duplicate_post_clone_post_link in the plugin. Compare those entry points with the reported WordPress 6.1.1 and plugin versions, then verify the documented behavior against the supplied reproduction and expected post IDs.