Code no longer working

Hi,

about half a year ago David kindly created a PHP snippet for me where I could add shortcode to every post on my blog and it was great! However this snippet no longer works for me is there anything I need to change?

add_filter( 'the_content', 'insert_content_after_paragraphs', 20 );
function insert_content_after_paragraphs( $content ) {
    $html = do_shortcode( '[your-shortcode]' );
    if ( is_single() && ! is_admin() ) {
        return prefix_insert_after_paragraph( $html, 3, $content );
    }
    return $content;
}
// Parent Function that makes the magic happen
function prefix_insert_after_paragraph( $insertion, $paragraph_id, $content ) {
    $closing_p = '</p>';
    $paragraphs = explode( $closing_p, $content );
    foreach ($paragraphs as $index => $paragraph) {
        if ( trim( $paragraph ) ) {
            $paragraphs[$index] .= $closing_p;
        }
        if ( $paragraph_id == $index + 1 ) {
            $paragraphs[$index] .= $insertion;
        }
    }
    return implode( '', $paragraphs );
}

Thank you!