I couldn't able user to a sharepoint group using Add user to Group wizard in k2 designer.  I used following steps to achieve mentioned task.

I created list in SharePoint with People Picker field.  I customized the form using smartforms and created workflow. 

In the form i'll select the group name and enter the user to be added to the group.

In the workflow,  i created group reference using create group reference wizard and here i'm filtering sharepoint group using Item Reference among all groups.

In the same way, I used create user reference wizard to filter the user using Item Reference.  Then I used Add User To group Wizard where i mapped the group reference and user reference.  But User is not added to the sharepoint group.  Whereas i am able to add user directly by selecting group and user. but bot able to add user if am using References.

Need suggestions on adding user to sharepoint group.  

Can anybody help me out in this regard?

Any help would be appreciated