One site disappeared from multisite after 4.5 upgrade

I have a multisite, the main site for which is therooftop.org
Then four sub sites are:
therooftop.org/uk
therooftop.org/us
therooftop.org/sa
therooftop.org/aus
I've just updated to WP 4.5 I got an Unable to update network error message. On looking at the sites the first four are ok but the last one (therooftop.org/aus) has the error message 'Unable to Connect to Database'

I've given you access to the site.

I feel I must point out that the SA and AUS sites are behind a coming soon page if not logged in.
If necessary I can delete the SA site and start again as it's just a clone of the UK site at the moment. If this is the best method to resolve this, how do I delete a site? Having said that, I'd sooner resolve the issue.

If you could help I'd be very grateful.

Many thanks,

John