Problems updating theme via Envato

Hi
I have the ‘Bimber’ theme installed on politics.scot, a subsite of unews.buzz.
I need to update it to the latest version, and have installed the Envato plugin and input a verifying token.

It then gets to the step of showing the orange box with ‘Update available’, but clicking on the link does nothing, it won’t begin the update. Also when I go to Themes section, it doesn’t offer the update option there.
I have enabled Support Access.
thanks, Neil.