ALSO POSTED ON WORDPRESS.ORG SITE - apologies but not sure which was the best place so posted on both.
My upgrade to latest version of Sydney has just failed so I have been forced to re-install.
Things are largely OK but I have an issue I am stuck on.
Previously I used:
in the Additional CSS section.
This is no longer working and none of the the new header controls seem to make my site header background white.