Content from Recently Added Blog Not Appearing in BuddyPress Activity Streams

I have a series of blogs and had my Buddypress community blog installed as the last in the series. (Blog ID 19 to be exact).

With this setup, all activity on the preceding blogs is correctly aggregating to the users' profile activity streams. All working well.

I have since added one more blog (blogID 20), and intend to continue adding as time and need arises.

My issue is that all activity on BlogID 20 is failing to show in the Community. All activity includes, blog posts and comments at this stage.

As far as I can tell, the blog setup settings are the same on blog20 as with blogs 1-18.

If anyone can enlighten me, I'd really appreciate it.

thanks for your help.