Integrating quickbooks not working

Integrating quickbooks not working

I have followed the tutorial at https://www.zoho.com/developer/help/scripting/quickbooks-add-record.html#ExampleCreate. After the installation there was already a default workflow rule 'Add Invoices Records to QuickBooks'. But when I create an invoice in zoho crm, corresponding invoice is not created in quickbooks. I even tried creating my own custom function for creating customer in quickbooks. But it is also not working. What am I doing wrong? How to debug the workflow custom function? Please help.