What am I missing in this hook?

I'm trying to update another DB on a different server when a subscription is updated, but I can't see what I'm missing here.

I've added this to site.inc.php

Code:

setup_plugin_hook('subscription_updated', 'updateap');

function updateap($member_id, $oldmember,$newmember){
 global $db;
 print "inupdate";
  $u = $db->get_user($member_id);
  //get_url($url, $post, $add_referrer)
  get_url("http://www.myurl.com/test.php");
  print_r($u);
  die;
    }

Stress that this is test code (which is why there is a print and die in there), but the test.php file will write info to a text file and so far nothing is happening.

If I change the member data here:
/amember/admin/users.php?action=edit_payment&payment_id=####&member_id=###

The call never seems to be made .. what am I missing?