EDI Instance ID Query not giving value at TN


We have a business scenario where TN receives EDI 850 Sales Order and triggers the business process.

TN is able to recognize the doc.type. But when TN try to form a conversation ID for the Transaction segment we are getting the error saying “Query [ST/BEG/BEG03] produced no BizDoc Instance Id [EDIFTN.000010.000104]”.(I have added an Instance ID Query ST/BEG/BEG03 at WmEDI page. I hope the syntax of the Query is also correct)
Transaction data has BEG03 value (Purchase Order #). I parsed the input EDI 850 using convertToValues and verified BEG03 holds a value.

What will be the problem?

We are using WmEDI 6.1. Do we need to install any fixes for this issue?( I don`t find any fixes for this issues )

Please let me know if you have any ideas.