BuddyPress.org

“activity private” – was just a general thought if you’d added a plugin or other custom code.

As I said before, without detailed info about your configuration, and your theme – it’s going to be difficult for anyone to help you on this one.

Does it only affect one user, or more than one?

Can you simulate it on one machine / browser – i.e. try activity for 2 users – do they both work?