does not recognize admin of subsite

I have Buddypress set up on a WordPress Multisite subsite. On that subsite, I have a user set up as an administrator/keymaster. He is a regular subscriber to the main site and is not a superadmin of the whole website. He runs into the private message limit. My own account is a superadmin of the site and I do not run into the private message limit. So it seems that when it is doing the check:

if (!user_can($current_user, ‘edit_users’))

it does it for the main site and not the subsite.