change status for reply author

i use ‘wpas_add_reply_public_after’ hook .
i’m need, change status to ‘open’ all tickets reply by author.

please help me .

e.g (dont work!):
add_action(‘wpas_add_reply_public_after’,’myfunc’);
function myfunc($post_id){
$post = get_post( $post_id );
update_post_meta( $post->post_parent, ‘_wpas_status’, ‘open’ );
}