To activate IPN, you need to provide a Notification URL in your account Profile (or include "notify_url" in your Web Accept button).
To test, try POSTing the FORM below to your script (madify "action" to point to your script):
<form method="post" action="http://www.mysite.com/ipn.cfm">
<input type="submit" name="" value="Test IPN">
<input type="hidden" name="payment_date" value="17:53:45 Nov 5, 2002 PST">
<input type="hidden" name="txn_type" value="web_accept">
<input type="hidden" name="last_name" value="Breitenbach">
<input type="hidden" name="item_name" value="">
<input type="hidden" name="payment_gross" value="0.01">
<input type="hidden" name="mc_currency" value="USD">
<input type="hidden" name="payment_type" value="instant">
<input type="hidden" name="verify_sign" value="AlWncXKLadIepzMosHhM.VWxC0Z6AZYI0ynXRnEUma0d3RMC.TXWaJro">
<input type="hidden" name="payer_status" value="unverified">
<input type="hidden" name="payer_email" value="pb-test@paypal.com">
<input type="hidden" name="txn_id" value="01G32341KC3727119">
<input type="hidden" name="first_name" value="Patrick">
<input type="hidden" name="quantity" value="1">
<input type="hidden" name="receiver_email" value="pb-sell@paypal.com">
<input type="hidden" name="payer_id" value="QGVDAFGZ9XHLJ">
<input type="hidden" name="payment_method" value="non_cc">
<input type="hidden" name="item_number" value="">
<input type="hidden" name="payment_status" value="Completed">
<input type="hidden" name="mc_gross" value="0.01">
<input type="hidden" name="custom" value="">
<input type="hidden" name="notify_version" value="1.4">
<input type="submit" value="Test IPN">
</form>
Patrick Breitenbach
PayPal, Inc.
Dev Net:
https://www.paypal.com/pdn