Hi Donald,
It sounds like the plugin hasn’t been updated for WP 3.1, which introduced the new Network Admin (where the BuddyPress dropdown is now found).
Follow the instructions in this post https://buddypress.org/community/groups/buddypress-group-email-subscription/forum/topic/change-admin_menu-to-network_admin_menu-for-wp-3-1-and-bp-1-2-8/ except do it on the file buddypress-auto-group-join/php/bp-auto-group-join-init.php. That should do the trick.
