"I am using the Fordson theme, which hasn't changed" – Do you mean that Fordson wasn't upgraded too? The theme would need to be upgraded from the 3.6 version to the 3.9 version. If this was upgraded, please tell us which version of Fordson is shown on the Plugins Overview page, for example:
General help
lost text visability of footer on version upgrade
This discussion has been locked so you can no longer reply to it.