My suggestions are all in the nature of "is it plugged in" because there are only a VERY few reasons why the dddw would fail to retrieve.

Please check that the DDDW is defined correctly in the PB application.
Ensure the Transaction object has been assigned to the dddw.
Ensure that the Transaction object is connected to the database at the time the Retrieve is issued.
Ensure that the deployed app has the rights to penetrate any firewall that might be in place, both on the client and on the server.


Good Luck!