I have created a new user group, and am trying to add multiple new users to the group. Under System Administration > User Groups, I click the "Add Multiple Users to a User Group" button. I'm then presented with a pull-down menu to select the user group to add the users to. However, the new group I have just created does not show up in the pull-down menu. What step am I missing to get my new group to show up in the list?