BuddyPress.org

I am admin for a fairly comprehensive site, still under construction.
I’m in the process of setting up the various sidebar widgets. They all work well except Sitewide notices, which has been set to be at the top of the right-hand sidebar, but it only displays a blank widget area, no title.
The widget setup screen/right-hand sidebar/’sitewide Notices’ just says “Preview unavailable”
Buddypress Settings/Private Messaging has been activated (ticked)
There’s no “This is a notice to all users” box in the front end Messages/Compose screen.

The site uses the latest versions of Buddypress and WordPress.
The current theme is Theme4Press’s Evolve Plus

I’ve tried deactivating all plugins except Buddypress.
I have tried switching the theme to Twenty Seventeen, but all to no avail!

Any help would be very much appreciated in getting the Sitewide Notices to work.