Authorize.net Responses

I am having a heck of a time getting the Authorize.net response codes to show up where I can work with them to determine what to do with my form once submitted.

In my onSubmit - before sending email:

<?php
global $MyPlugins;

if($MyPlugins->cf_Authorize_dotnet['response_code'] != 'Approved'){
$emails[0]->enabled = 0;

$MyPlugins is always empty... what the heck? I know I'm missing something simple here. This is on J1.5 with CF 3.1 RC5.3

Thanks,
Andy