nextpage tag Not working

Hi, I know this has been discussed many times in the past but I could not find a resolution of my problem.

Objective: I am trying to break one of my post into multiple pages.

What I have done so far:
1. I have put in <!-nextpage-> at the end of the paragraph where I want to break the page. [ URL of the page here ]
2. I have added wp_link_pages tag to the single.php file. Here is a snapshot of what I added –

<?php if ( have_posts() ) while ( have_posts() ) : the_post(); ?>
<?php get_template_part( ‘content’, get_post_format() ); ?>
<?php get_template_part( ‘nav’, ‘post-single’ ); ?>
<?php comments_template( ”, true ); ?>
<?php wp_link_pages(array(‘before’ => ‘<p>Pages: ‘, ‘after’ => ‘</p>’, ‘next_or_number’ => ‘number’)); ?>
<?php endwhile; // end of the loop. ?>

But nothing changed!! Am I missing something? I am not good with coding. Please help.