I tried to get the next and previous URL, and create a navigation. But it seems to only retrieve the permalink from the two first posts (but not the others recents posts).

I have 5 posts (ID = 25, 86, 80, 75, 45). When I am on the first post (ID = 25) and I click on previous post, I am going to post ID = 45, and after when I click on previous it stay on the same page.

<?php 
  if (have_posts()) : while (have_posts()) : the_post();

  $prev = get_permalink(get_adjacent_post(false,'',false));
  $next = get_permalink(get_adjacent_post(false,'',true)); ?>

  <li class="post-link">
    <a class="prev" href="<?php echo $prev; ?>">
      <span class="icon-prev"></span>
    </a>
  </li>
  
  <li class="post-link">
    <a class="next" href="<?php echo $next; ?>">
      <span class="icon-next"></span>
    </a>
  </li>

<?php endwhile; endif; get_footer(); ?>

I also tried to put the code after the while loop.

I tried to get the next and previous URL, and create a navigation. But it seems to only retrieve the permalink from the two first posts (but not the others recents posts).

I have 5 posts (ID = 25, 86, 80, 75, 45). When I am on the first post (ID = 25) and I click on previous post, I am going to post ID = 45, and after when I click on previous it stay on the same page.

<?php 
  if (have_posts()) : while (have_posts()) : the_post();

  $prev = get_permalink(get_adjacent_post(false,'',false));
  $next = get_permalink(get_adjacent_post(false,'',true)); ?>

  <li class="post-link">
    <a class="prev" href="<?php echo $prev; ?>">
      <span class="icon-prev"></span>
    </a>
  </li>
  
  <li class="post-link">
    <a class="next" href="<?php echo $next; ?>">
      <span class="icon-next"></span>
    </a>
  </li>

<?php endwhile; endif; get_footer(); ?>

I also tried to put the code after the while loop.

Update I solved the problem. When I published my posts, they had all the same date, so it displayed only one post from this date. I changed with a different day date, and it works! My bad.