e-Commerce with Paypal checkout express: Broken Flow

Dear WordPress users,

My checkout flow breaks on the “Confirm Payment” step. Clicking on that button doesn’t do anything visible to me.

Let me elaborate. I have WP 3.1.4 with e-Commerce 3.8.7.2 and the PayPal Checkout Express selected as the only gateway, running through the Paypal sandbox.

I am able to add a product in the shopping card and check out, up to the point where PayPal returns me to the “Transaction Results” page on my site. This page contains a purchase summary and a “Confirm Payment” button beneath it. Clicking on this button brings me back to the same page content — although the page URL seems to change (some name/value pairs following the ‘?’ disappear). Clicking again the button will benefit me nothing from this point onward.

Going to “Store” -> “Transaction Results” (from the pop-up menu) loads the exact same page. Going to “Store” -> “Your Account” (from the same menu) brings a list with my purchase(s), where I can see that my last purchase`s order status is “Incomplete Sale”. Logging as admin, I can confirm the purchase is listed as “incomplete sale”.

Going to PayPal, though, I can see the purchase was rather successful, and the payment accepted.

I am not sure what am I doing wrong. Is the PayPal’s IPN (instant payment notification) supposed to play any role here? For I haven’t been able to issue an IPN from the PayPal sandbox (this functionality is rather buggy).

Should I consider testing using “real life” transactions? That will cost me real money, though, as PayPal charges for each transaction…

Thank you for having read this, and thank you a lot for any help you can provide.

Claudius