Banging head against wall here with Live Chat: have network

Banging head against wall here with Live Chat: have network installed and activated on main site. Functions perfectly for Admin - I see the green traffic light in top bar showing Chat active (Status available).

But, when I log in as another (test) user on another computer, Chat bottom right window displays message 'you must login to participate in chat'.

I've double and triple checked authentication settings in Chat 'Settings Site' - I definitely have WordPress user, Network user and even Public user checked. I can't see any other place I'd need to authenticate the logged-in user to be able to use Chat.

What am I missing? Cheers!

PS it's a Buddypress site.