Sender Interface name not appearing in dropdown list of RWB- SAP PI 7.4-Dual

Hello All,

Currently i am using SAP PI 7.4 dual stack system. As part of Unit testing I have to post message from RWB to target system. Hence i went to Testing tab--->Send Test Message option.

But heere I can't enter the Sender Interface name in a free text manner (like how we used to do on 7.1) instead i have to select the Sender Interface name from the drop down menu. But unfortunately the dropdown doesn't have the Sender interface that i am trying to post message.

Can you please tell me what setting is required to get my Sender interface name in the dropdown

Thanks,

Moorthy