Hi. Just realised that the above code is incorrect as that doesn’t get the current category’s ID. This should work…
<?php
$category = get_category( get_query_var( 'cat' ) );
$cat_id = $category->cat_ID;
if(get_field('cat_image', 'category_'. $cat_id .'')) { ?>
<?php the_field('cat_image', 'category_'. $cat_id .''); ?>
<?php endif; ?>