Showing Commenter Avatars

My blog is not showing avatars of commenters. I think something has changed that necessitates a change to my theme’s comments.php file.

It has :

<div class="comments">
    <h3><?php comments_number('No Responses', 'One Response', '% Responses' );?> to “<?php the_title(); ?>”</h3>
    <ol class="commentlist">
    <?php foreach ($comments as $comment) : ?>
        <li class="<?php echo $oddcomment; ?>" id="comment-<?php comment_ID() ?>">
            <?php comment_text() ?>
            <p class="commentmetadata">
                <?php echo get_avatar( $id_or_email, $size = '32'); ?>
                <small>
                <cite><?php comment_author_link() ?></cite> said this on
                <?php if ($comment->comment_approved == '0') : ?>
                <em>Your comment is awaiting moderation.</em>
                <?php endif; ?>
                <a href="#comment-<?php comment_ID() ?>" title=""><?php comment_date('F jS, Y') ?> at <?php comment_time() ?></a> <?php edit_comment_link('edit','(',')'); ?>
                </small>
            </p>
        </li>
    <?php /* Changes every other comment to a different class */
        if ('alt' == $oddcomment) $oddcomment = '';
        else $oddcomment = 'alt';
    ?>
    <?php endforeach; /* end for each comment */ ?>
    </ol>
</div>

I tried replacing:
<?php echo get_avatar( $id_or_email, $size = '32'); ?>
with
<?php wp_list_comments( array( 'avatar_size' => '50' ) ); ?>

Gravatars appeared, but I do not know how to integrate this into the original structure …. I can’t just replace that one line (comments repeated ad infinitum).

Any help in fixing up this PHP would be appreciated!

https://www.ads-software.com/extend/plugins/comments/