what code do you use to display the gallery? and what is your gallery-fieldname?
gallery is an array, that means you need a foreach loop like this to show the images inside that array:
<?php
$images = get_field('gallery');
if( $images ): ?>
<ul>
<?php foreach( $images as $image ): ?>
<li>
<a href="<?php echo $image['url']; ?>">
<img src="<?php echo $image['sizes']['thumbnail']; ?>" alt="<?php echo $image['alt']; ?>" />
</a>
<p><?php echo $image['caption']; ?></p>
</li>
<?php endforeach; ?>
</ul>
<?php endif; ?>
