Issue in assigning Requestioner for shop on behalf

Hi All,

We are in SRM7.13 SP01 and need to enable shop on behalf functionality for shopping cart, i know that to enable that we have to assign Reuqestioner attribute with the user on whoes behalf other person can shop. But in our issue is that I am not able to search any users in Requestioner attributes and have tries with * also . I am not able to select any Good recipent in the shoppin Cart.It will be greate if you can provide me the information i'm missing to enable this functionality.

Thanks,

Ankur