[Lynne]

You need to give people time to reply....

You need to have this set to Yes in your Primary Usergroup:
Allow Users to have Member Groups (Sets whether or not permissions from the user's member (secondary) user group memberships are inherited or not)

Allow Users to have Member Groups
This option must be set to "Yes" if secondary (member) groups are to have any effect on the permissions of users whose primary group is this group.

Secondary groups serve no purpose if this option is set to "No". The only reason this option should be set to "No" is if this group is a banned group, in which case you don't want secondary group memberships to override the null access of the banned group.