If you have noticed that your first export from Billings Pro to MoneyWorks is fine, but the second time you export, you get the following error as found in your Custom Plug-Ins folder:
For Line 1: The reference "101" does not uniquely identify any outstanding invoice for "project name."
In this case, after the first export, MoneyWorks fails to send information to Billings Pro about the data being already present. So, when you export the second time, since the same data is already in MoneyWorks, the export fails.
To solve this, working from Billings Pro,
- Open the export tool (File > Export > To MoneyWorks 6).
- Select the items (either a retainer/invoice/payment).
- Right-click and choose Mark as "sent" from the contextual menu and then export.