Check that the “project_galleries” field in ACF is set up as a REPEATER, and inside it, “project_gallery” is configured as a gallery.
To work with Gutenberg blocks, you can try using the “get_field()” function instead of “have_rows()”. Try this:
<?php
$galleries = get_field('project_galleries');
if($galleries):
foreach($galleries as $gallery):
$images = $gallery['project_gallery'];
if($images):
foreach($images as $image): ?>
<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>
<?php endforeach;
endif;
endforeach;
endif; ?>
