F4 Search option not available through webgui / Tr. iView

We have NW Portal 7.31 and ECC 6 ehp 6 in our Landscape. We have created a transaction iview so that some portal users can create sales order (VA01) using Portal.

This tr. iview uses webgui in the backend.

But pressing F4 to choose values in various fields is not working. We cannot choose any option.

Please find attached the screenshot.

Thanks,

Gaurav