Content not rendering after <InnerBlocks />

block.php

<?php
$allowed_blocks = array(
  'core/heading',
);

$template = array(
  array(
    'core/heading',
    array(
      'level'     => 2,
      'textColor' => 'white',
      'content'   => __( 'Add your heading', 'text-domain' ),
    ),
  ),
);

echo '<InnerBlocks allowedBlocks="' . esc_attr( wp_json_encode( $allowed_blocks ) ) . '" template="' . esc_attr( wp_json_encode( $template ) ) . '" />';

if ( $is_preview ) :
  ?>
  <div class="admin-notice">
    <?php esc_html_e( 'Your signup form will appear below.', 'text-domain' ); ?>
  </div>
  <?php
endif;
?>

<div>
  <p>Some static content rendered here</p>
</div>