BuddyPress.org

The admin says “cheatin, uh?”, I believe, when you try to submit a form or follow a link with a nonce belonging to another user.

@Boniu Make sure you have a fully working multisite before you install BuddyPress. i.e. permalinks, comments, and so on. To try to resurrect your site, remove the /plugins/ folder then visit /wp-admin/ again.