change the opening if statement in your function (assuming your checkbox field has a key of field_asd856f4a8sdf
if( ( $_POST['post_status'] == 'publish' ) &&
( $_POST['original_post_status'] != 'publish' )
( !empty( $_POST['fields']['field_asd856f4a8sdf'] )
) {
check the source code after your page loads to determine the acf key. it will look like that one i’ve put there, even though i made that one up.
