First, thank you for your Page-Links Plus purchase.
Second, we're happy to help you resolve this issue, as we're able. Two initial troubleshooting suggestions follow:
First, make sure your theme contains the
wp_link_pages function (http://codex.wordpress.org/Function_Reference/wp_link_pages). This function usually appears at the bottom of a theme's page.php/single.php template or in your footer.php file.
You won't need to use any parameters in the function, since you can manage these via PLP. As such, a simple
<?php wp_link_pages(); ?> will suffice.
Second, make sure you/the theme are wrapping your content in best-practices HTML tags (e.g.,
<ul>, &c.). Page-Links Plus leverages those tags in a number of ways.
If neither of these theme adjustments fixes your issue, please let me know.
Thanks again for your purchase.