WordPress plugin admin ajax not working anymore

Solution:

I would recommend using wordpress standard ajax for that instead of making an ajax call to your own php file:

add_action('wp_ajax_yourfunction', 'yourfunction');
add_action('wp_ajax_nopriv_yourfunction', 'yourfunction');

function nsds_change_password() { 
//your functional part goes here
}

Anf then in ajax call use admin ajax url which can be output beforehand like this:

<script type='text/javascript'> var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>"; </script>

and the use ajaxurl as a variable and set additonal action parameter wich will be your function name.