Where are these fields located? What post? Options Page?
What page is being shown? What template is being used? Post? Archive?
Try included the post ID of the post the fields are connected to.
// set $post_id to the location of the repeater field
if ( have_rows( 'hero_slide', $post_id ) ) :
while ( have_rows( 'hero_slide', $post_id ) ) : the_row();