I think that ACF PRO v5.1.7.1 and WordPress v4.5.1. has some mismatch with Flexible Content Fields. It seem like plugin doesn’t get rows from flexible content, everything after “if( have_rows(‘flex_test’)” stopped displaying.
Heres my test code:
<section id="section-flex" class="section">
<?php if( have_rows('flex_test') ): ?>
<?php while ( have_rows('flex_test') ) : the_row();
if( get_row_layout() == 'test' ): ?>
<h3><?php the_sub_field('title'); ?></h3>
<?php endif; endwhile; ?>
<?php endif; ?>
</section>
<!– EDIT –>
Solved: There was some error in database, after updating again the WP Flexible fields started to work!
Glad you got this working.