SSL Security issue on my checkout page

Hi, I am trying to get my products on Google Merchant Centre and part of their policy is that I have a secured ‘checkout’ page. I purchased an SSL certificate and forced WooCommerce to go to https:// on the checkout page. Google keep failing me because the page is not totally secure. I tried disabling any popups or plugins on that page but it still didn’t work. It seems to be an issue with my site logo image that is causing the security issue.

Please would you have a look if you go to westcoasthammocks.com.au/superjumbo and go through the shopping process until you get to the checkout page. You can then click the white folded page icon on the far left of the address bar to see the security issue. Any help is greatly appreciated.