I’ve found a solution so hopefully this helps the others who have had this problem…
The key is to install group forums before changing buddypress onto a secondary site/blog.
@willhendy,
I have this issue as well. I have a primary site with BuddyPress enabled and configured and several subsites with BuddyPress enabled and configured.
Did you Network Activate BuddyPress or activate it on a site by site basis?
If you network activate BuddyPress is it automatically setup (but not configured) on all subsites.
@elangley
I installed a fresh copy of WordPress Multisite and added the BuddyPress plugin and Network Activated.
On the primary site I configured BuddyPress and then clicked the “Install Group Forums” button. I still received the “You do not have sufficient permissions to access this page.” error.
@elangley
~eric