Output type not showing automatically

Hi All,

I'm creating IDocs thru Message control for Purchase Order ME21N. When I create a PO, after filling all the heade and item details on the screen of ME21N for a particular vendor, I go to 'Messages' tab but can't find the output, medium, partner etc on that screen. I manually enter the details here and IDoc is created.

Earlier, this ouput detail was populating automatically but now It's not coming. I checked all settings in NACE, WE20 etc for that particular vendor but I couldn't find any clue.

Please help me. It's very urgent.