Paying an Affiliate with Marketpress purchase

I have the Affiliate plugin and Marketpress working great. However, with Marketpress in sandbox mode, Affiliate doesn't recognize the sale (at least not the I have it configured). The sale is going through Paypal fine, and I get an email with the purchase information, it just doesn't credit the affiliate in the Affiliate dashboard. Is there a way to test that I have it configured correctly prior to going live, or did I mess up something to connect the two plugins.
Thanks.