I can’t access Customise option on Vantage Theme

I need to change the Posts Page to the Blog Page. Obviously I go onto Customise but nothing comes up. The options down the left hand side are blank and the website does not show up in the preview box!

This has only happened since the new update of the theme, is there anything I can do to sort this or is this an error everybody is having with this theme?

URL: http://busylizziepa.co.uk/