Failing to render the Pay Dialog before Facebook's 9/12 breaking changes

Failing to render the Pay Dialog before Facebook's 9/12 breaking changes

I'm attempting to migrate my app's Facebook Payment before the 9/12
breaking changes deadline, and am having issues properly rendering the Pay
Dialog.
I have the product object set up per the new Payments' requirements, and
have modified the FB.ui() key/values as necessary:
onPlaceOrder : function(order_info, swfOrderCallback) {
var onOrderPlaced = function(data) {
if(swfOrderCallback) {
MOGA.callMovieFunction('swfContainer', swfOrderCallback,
data);
}
};
// calling the API ...
try {
FB.ui({
method : 'pay',
method : 'purchaseitem',
product :
'http://test37.d.gaiaonline.com/fbapps/monsterpets/currency/',
quantity : 1
//order_info : order_info
}, onOrderPlaced);
} catch (err) {
}
}
When I bring up the $-to-in-game-currency dialog, the modal that players
use to select the product pops up as it should, but clicking Continue does
not bring up the Pay Dialog as expected.
Clicking continue pings
https://apps.facebook.com/fbml/ajax/dialog/purchaseitem?product=http%3A%2F%2Ftest37.d.gaiaonline.com%2Ffbapps%2Fmonsterpets%2Fcurrency%2F&quantity=1&e2e=%7B%7D&app_id=161781587358197&locale=en_US&sdk=joey&display=async&redirect_uri=https%3A%2F%2Ftest37.d.gaiaonline.com%2Ffbapps%2Fmonsterpets%2F&__d=1&__user=6703306&__a=1&__dyn=7n8apij348FUSt2u5KKDKaExEW9K9W&__req=1c
with the parameters
e2e {}
locale en_US
product http://test37.d.gaiaonline.com/fbapps/monsterpets/currency/
quantity 1
redirect_uri https://test37.d.gaiaonline.com/fbapps/monsterpets/
sdk joey
and receives as a response for
(;;);{"__ar":1,"payload":{"hiding":1},"bootloadable":{},"ixData":[]}.
The callback in onPlaceOrder (the var onOrderPlaced) contains
onPlaceOrder, which results in the no Pay dialog and the modal staying
open.
Does anyone have any idea what code or process needs to change to open the
Pay Dialog?