Cannot activate user accounts manually

Last week, I could do this just fine; however, today when I try to "manage signups" and activate a user account, I get the "you do not have sufficient permissions to access this page" message. I am logged in as super-admin.

I am not sure exactly when the issue began, so I'm having a hard time determining what might be causing the issue. I did enable BP Multi-Network recently, so it may be connected to that? I definitely need that feature to be enabled, so going back is not an option. Otherwise, I have no idea what I may have done to cause this.

I have granted support access so you can have a look need be.