oe_order_pub.process_order returned an error code but no error message

Hi

     When I used API oe_order_pub.process_order to creare a Sales Order, the API returned an error code 'E', and the error message is FND.  This is :

     x_return_status='E',

    x_msg_count=1,

   x_msg_data ='FND'.

    In fact, the sales person is inactive results in this issue.  I also used OE_MSG_PUB.GET to get its error message. But still returned 'FND'.  If there was no error message, I could not find what caused this problem.

   How could I get the error messages? 

Thanks.

Allen