Quote Originally Posted by pennylane View Post
I'm using ZenCart 1.3.8a and am using PayPal Website Payments Standard for all transactions. It is set up so that the customer returns to my site, to a Thank You page, after payment on PayPal has been made.
Oh ... I misread that you're using Standard. Now I see why you were intent on using the PayPal code they suggested, even though it's not suitable for Zen Cart sites.
It's very complicated to get Standard to work reliably ... especially with affiliate programs.
It's MAJORLY simpler if you're using Express Checkout. ie: if you turn off Standard and turn on Express (and configure it: http://www.zen-cart.com/getpaypal ), your affiliate code will work fine.

What's happening now is likely that you're testing on a site that's not getting proper communication back from PayPal to release your orders, and thus the affiliate system isn't able to produce any information because there's nothing for it to pass forward. I'm pretty sure it's failing because it's seeing an order-number of 0 because PayPal's background IPN process isn't completing properly on your site.
While you should still get the IPN process fixed (http://www.zen-cart.com/wiki/index.php/PayPal ) in order to have refunds etc reflected in your store, I strongly recommend using Express Checkout instead.